add gaussian fitting for better background estimation

src/FOC_reduction.py

@@ -131,28 +131,29 @@ def main():
     display_crop = False
     # Error estimation
     error_sub_type = 'freedman-diaconis'   #sqrt, sturges, rice, scott, freedman-diaconis (default) or shape (example (15,15))
+    subtract_error = False
     display_error = False
     # Data binning
     rebin = True
-    pxsize = 0.10
+    pxsize = 10
-    px_scale = 'arcsec'         #pixel, arcsec or full
+    px_scale = 'pixel'         #pixel, arcsec or full
     rebin_operation = 'sum'     #sum or average
     # Alignement
     align_center = 'image'          #If None will align image to image center
     display_data = False
     # Smoothing
     smoothing_function = 'combine'  #gaussian_after, weighted_gaussian_after, gaussian, weighted_gaussian or combine
-    smoothing_FWHM = 0.20           #If None, no smoothing is done
+    smoothing_FWHM = None           #If None, no smoothing is done
     smoothing_scale = 'arcsec'      #pixel or arcsec
     # Rotation
     rotate_stokes = True
     rotate_data = False             #rotation to North convention can give erroneous results
     # Final crop
     crop = False                    #Crop to desired ROI
-    final_display = False
+    final_display = True
     # Polarization map output
     figname = 'NGC1068_FOC'         #target/intrument name
-    figtype = '_c_FWHM020'    #additionnal informations
+    figtype = '_bin10px'    #additionnal informations
     SNRp_cut = 5.    #P measurments with SNR>3
     SNRi_cut = 50.   #I measurments with SNR>30, which implies an uncertainty in P of 4.7%.
     step_vec = 1    #plot all vectors in the array. if step_vec = 2, then every other vector will be plotted
@@ -173,7 +174,7 @@ def main():
     # Estimate error from data background, estimated from sub-image of desired sub_shape.
     background = None
     if px_scale.lower() not in ['full','integrate']:
-        data_array, error_array, headers, background = proj_red.get_error(data_array, headers, error_array, sub_type=error_sub_type, display=display_error, savename=figname+"_errors", plots_folder=plots_folder, return_background=True)
+        data_array, error_array, headers, background = proj_red.get_error(data_array, headers, error_array, sub_type=error_sub_type, subtract_error=subtract_error, display=display_error, savename=figname+"_errors", plots_folder=plots_folder, return_background=True)
 
     # Align and rescale images with oversampling.
     data_array, error_array, headers, data_mask = proj_red.align_data(data_array, headers, error_array=error_array, background=background, upsample_factor=10, ref_center=align_center, return_shifts=False)

src/comparison_Kishimoto.py

@@ -70,7 +70,7 @@ im0 = ax.imshow(data_S['I']*convert_flux,norm=LogNorm(data_S['I'][data_S['I']>0]
 #im0 = ax.imshow(data_S['P']*100.,vmin=0.,vmax=100.,origin='lower',cmap='inferno',label=r"$P$ through this pipeline")
 #im0 = ax.imshow(data_K['PA'],vmin=0.,vmax=360.,origin='lower',cmap='inferno',label=r"$\theta_P$ through Kishimoto's pipeline")
 #im0 = ax.imshow(data_S['PA'],vmin=0.,vmax=360.,origin='lower',cmap='inferno',label=r"$\theta_P$ through this pipeline")
-quiv0 = ax.quiver(data_S['X'],data_S['Y'],data_S['xy_U'],data_S['xy_V'],units='xy',angles='uv',scale=0.5,scale_units='xy',pivot='mid',headwidth=0.,headlength=0.,headaxislength=0.,width=0.1,color='b',alpha=0.75, label="PA through this pipeline")
+quiv0 = ax.quiver(data_S['X'],data_S['Y'],data_S['xy_U'],data_S['xy_V'],units='xy',angles='uv',scale=0.5,scale_units='xy',pivot='mid',headwidth=0.,headlength=0.,headaxislength=0.,width=0.2,color='b',alpha=0.75, label="PA through this pipeline")
 quiv1 = ax.quiver(data_K['X'],data_K['Y'],data_K['xy_U'],data_K['xy_V'],units='xy',angles='uv',scale=0.5,scale_units='xy',pivot='mid',headwidth=0.,headlength=0.,headaxislength=0.,width=0.1,color='r',alpha=0.75, label="PA through Kishimoto's pipeline")
 
 ax.set_title(r"$SNR_P \geq 5 \; & \; SNR_I \geq 30$")

src/lib/background.py

@@ -2,7 +2,7 @@
 Library function for background estimation steps of the reduction pipeline.
 
 prototypes :
-    - display_bkg(data, background, std_bkg, headers, histograms, bin_centers, rectangle, savename, plots_folder)
+    - display_bkg(data, background, std_bkg, headers, histograms, binning, rectangle, savename, plots_folder)
         Display and save how the background noise is computed.
     - bkg_hist(data, error, mask, headers, sub_shape, display, savename, plots_folder) -> n_data_array, n_error_array, headers, background)
         Compute the error (noise) of the input array by computing the base mode of each image.
@@ -18,8 +18,20 @@ from matplotlib.colors import LogNorm
 from matplotlib.patches import Rectangle
 from datetime import datetime
 from lib.plots import plot_obs
+from scipy.optimize import curve_fit
 
-def display_bkg(data, background, std_bkg, headers, histograms=None, bin_centers=None, rectangle=None, savename=None, plots_folder="./"):
+def gauss(x, *p):
+    N, mu, sigma = p
+    return N*np.exp(-(x-mu)**2/(2.*sigma**2))
+
+def gausspol(x, *p):
+    N, mu, sigma, a, b, c, d = p
+    return N*np.exp(-(x-mu)**2/(2.*sigma**2)) + a*np.log(x) + b/x + c*x + d
+
+def bin_centers(edges):
+    return (edges[1:]+edges[:-1])/2.
+
+def display_bkg(data, background, std_bkg, headers, histograms=None, binning=None, coeff=None, rectangle=None, savename=None, plots_folder="./"):
     plt.rcParams.update({'font.size': 15})
     convert_flux = np.array([head['photflam'] for head in headers])
     date_time = np.array([headers[i]['date-obs']+';'+headers[i]['time-obs']
@@ -52,12 +64,15 @@ def display_bkg(data, background, std_bkg, headers, histograms=None, bin_centers
     if not(histograms is None):
         filt_obs = {"POL0":0, "POL60":0, "POL120":0}
         fig_h, ax_h = plt.subplots(figsize=(10,6), constrained_layout=True)
-        for i, (hist, bins) in enumerate(zip(histograms, bin_centers)):
+        for i, (hist, bins) in enumerate(zip(histograms, binning)):
             filt_obs[headers[i]['filtnam1']] += 1
             ax_h.plot(bins,hist,'+',color="C{0:d}".format(i),alpha=0.8,label=headers[i]['filtnam1']+' (Obs '+str(filt_obs[headers[i]['filtnam1']])+')')
             ax_h.plot([background[i],background[i]],[hist.min(), hist.max()],'x--',color="C{0:d}".format(i),alpha=0.8)
+            if not(coeff is None):
+                ax_h.plot(bins,gausspol(bins,*coeff[i]),'--',color="C{0:d}".format(i),alpha=0.8)
         ax_h.set_xscale('log')
-        ax_h.set_xlim([background.mean()*1e-2,background.mean()*1e2])
+        ax_h.set_ylim([0.,np.max([hist.max() for hist in histograms])])
+        ax_h.set_xlim([np.min(background)*1e-2,np.max(background)*1e2])
         ax_h.set_xlabel(r"Count rate [$s^{-1}$]")
         ax_h.set_ylabel(r"Number of pixels in bin")
         ax_h.set_title("Histogram for each observation")
@@ -97,8 +112,128 @@ def display_bkg(data, background, std_bkg, headers, histograms=None, bin_centers
 
     plt.show()
 
+def sky_part(img):
+    rand_ind = np.unique((np.random.rand(np.floor(img.size/4).astype(int))*2*img.size).astype(int)%img.size)
+    rand_pix = img.flatten()[rand_ind]
+    # Intensity range
+    sky_med = np.median(rand_pix)
+    sig = np.min([img[img<sky_med].std(),img[img>sky_med].std()])
+    sky_range = [sky_med-2.*sig, sky_med+sig]
 
-def bkg_hist(data, error, mask, headers, sub_type=None, display=False, savename=None, plots_folder=""):
+    sky = img[np.logical_and(img>=sky_range[0],img<=sky_range[1])]
+    return sky, sky_range
+
+def bkg_estimate(img, bins=None, chi2=None, coeff=None):
+    if bins is None or chi2 is None or coeff is None:
+        bins, chi2, coeff = [8], [], []
+    else:
+        try:
+            bins.append(int(3./2.*bins[-1]))
+        except IndexError:
+            bins, chi2, coeff = [8], [], []
+    hist, bin_edges = np.histogram(img[img>0], bins=bins[-1])
+    binning = bin_centers(bin_edges)
+    peak = binning[np.argmax(hist)]
+    bins_fwhm = binning[hist>hist.max()/2.]
+    fwhm = bins_fwhm[-1]-bins_fwhm[0]
+    p0 = [hist.max(), peak, fwhm, 1e-3, 1e-3, 1e-3, 1e-3]
+    try:
+        popt, pcov = curve_fit(gausspol, binning, hist, p0=p0)
+    except RuntimeError:
+        popt = p0
+    chi2.append(np.sum((hist - gausspol(binning,*popt))**2)/hist.size)
+    coeff.append(popt)
+    return bins, chi2, coeff
+
+def bkg_fit(data, error, mask, headers, subtract_error=True, display=False, savename=None, plots_folder=""):
+    """
+    ----------
+    Inputs:
+    data : numpy.ndarray
+        Array containing the data to study (2D float arrays).
+    error : numpy.ndarray
+        Array of images (2D floats, aligned and of the same shape) containing
+        the error in each pixel of the observation images in data_array.
+    mask : numpy.ndarray
+        2D boolean array delimiting the data to work on.
+    headers : header list
+        Headers associated with the images in data_array.
+    display : boolean, optional
+        If True, data_array will be displayed with a rectangle around the
+        sub-image selected for background computation.
+        Defaults to False.
+    savename : str, optional
+        Name of the figure the map should be saved to. If None, the map won't
+        be saved (only displayed). Only used if display is True.
+        Defaults to None.
+    plots_folder : str, optional
+        Relative (or absolute) filepath to the folder in wich the map will
+        be saved. Not used if savename is None.
+        Defaults to current folder.
+    ----------
+    Returns:
+    data_array : numpy.ndarray
+        Array containing the data to study minus the background.
+    headers : header list
+        Updated headers associated with the images in data_array.
+    error_array : numpy.ndarray
+        Array containing the background values associated to the images in
+        data_array.
+    background : numpy.ndarray
+        Array containing the pixel background value for each image in
+        data_array.
+    """
+    n_data_array, n_error_array = deepcopy(data), deepcopy(error)
+    error_bkg = np.ones(n_data_array.shape)
+    std_bkg = np.zeros((data.shape[0]))
+    background = np.zeros((data.shape[0]))
+    histograms, binning = [], []
+    
+    for i, image in enumerate(data):
+        #Compute the Count-rate histogram for the image
+        sky, sky_range = sky_part(image[image>0.])
+
+        bins, chi2, coeff = bkg_estimate(sky)
+        while bins[-1]<256:
+            bins, chi2, coeff = bkg_estimate(sky, bins, chi2, coeff)
+        hist, bin_edges = np.histogram(sky, bins=bins[-1])
+        histograms.append(hist)
+        binning.append(bin_centers(bin_edges))
+        chi2, coeff = np.array(chi2), np.array(coeff)
+        weights = 1/chi2**2
+        weights /= weights.sum()
+
+        bkg = np.sum(weights*coeff[:,1])
+       
+        error_bkg[i] *= bkg
+       
+        # Quadratically add uncertainties in the "correction factors" (see Kishimoto 1999)
+        #wavelength dependence of the polariser filters
+        #estimated to less than 1%
+        err_wav = data[i]*0.01
+        #difference in PSFs through each polarizers
+        #estimated to less than 3%
+        err_psf = data[i]*0.03
+        #flatfielding uncertainties
+        #estimated to less than 3%
+        err_flat = data[i]*0.03
+
+        n_error_array[i] = np.sqrt(n_error_array[i]**2 + error_bkg[i]**2 + err_wav**2 + err_psf**2 + err_flat**2)
+        
+        #Substract background
+        if subtract_error:
+            n_data_array[i][mask] = n_data_array[i][mask] - bkg
+            n_data_array[i][np.logical_and(mask,n_data_array[i] <= 0.01*bkg)] = 0.01*bkg
+ 
+        std_bkg[i] = image[np.abs(image-bkg)/bkg<1.].std()
+        background[i] = bkg
+
+    if display:
+        display_bkg(data, background, std_bkg, headers, histograms=histograms, binning=binning, coeff=coeff, savename=savename, plots_folder=plots_folder)
+    return n_data_array, n_error_array, headers, background
+
+
+def bkg_hist(data, error, mask, headers, sub_type=None, subtract_error=True, display=False, savename=None, plots_folder=""):
     """
     ----------
     Inputs:
@@ -144,7 +279,7 @@ def bkg_hist(data, error, mask, headers, sub_type=None, display=False, savename=
     error_bkg = np.ones(n_data_array.shape)
     std_bkg = np.zeros((data.shape[0]))
     background = np.zeros((data.shape[0]))
-    histograms, bin_centers = [], []
+    histograms, binning, coeff = [], [], []
     
     for i, image in enumerate(data):
         #Compute the Count-rate histogram for the image
@@ -167,10 +302,20 @@ def bkg_hist(data, error, mask, headers, sub_type=None, display=False, savename=
         
         hist, bin_edges = np.histogram(np.log(image[n_mask]),bins=n_bins)
         histograms.append(hist)
-        bin_centers.append(np.exp((bin_edges[:-1]+bin_edges[1:])/2))
+        binning.append(np.exp(bin_centers(bin_edges)))
+        
         #Take the background as the count-rate with the maximum number of pixels
-        hist_max = bin_centers[-1][np.argmax(hist)]
+        #hist_max = binning[-1][np.argmax(hist)]
-        bkg = np.sqrt(np.sum(image[np.abs(image-hist_max)/hist_max<0.5]**2)/image[np.abs(image-hist_max)/hist_max<0.5].size)
+        #bkg = np.sqrt(np.sum(image[np.abs(image-hist_max)/hist_max<0.5]**2)/image[np.abs(image-hist_max)/hist_max<0.5].size)
+        
+        #Fit a gaussian to the log-intensity histogram
+        bins_fwhm = binning[-1][hist>hist.max()/2.]
+        fwhm = bins_fwhm[-1]-bins_fwhm[0]
+        p0 = [hist.max(), binning[-1][np.argmax(hist)], fwhm, 1e-3, 1e-3, 1e-3, 1e-3]
+        popt, pcov = curve_fit(gausspol, binning[-1], hist, p0=p0)
+        coeff.append(popt)
+        bkg = popt[1]
+        
         error_bkg[i] *= bkg
        
         # Quadratically add uncertainties in the "correction factors" (see Kishimoto 1999)
@@ -187,6 +332,7 @@ def bkg_hist(data, error, mask, headers, sub_type=None, display=False, savename=
         n_error_array[i] = np.sqrt(n_error_array[i]**2 + error_bkg[i]**2 + err_wav**2 + err_psf**2 + err_flat**2)
         
         #Substract background
+        if subtract_error:
             n_data_array[i][mask] = n_data_array[i][mask] - bkg
             n_data_array[i][np.logical_and(mask,n_data_array[i] <= 0.01*bkg)] = 0.01*bkg
  
@@ -194,11 +340,11 @@ def bkg_hist(data, error, mask, headers, sub_type=None, display=False, savename=
         background[i] = bkg
 
     if display:
-        display_bkg(data, background, std_bkg, headers, histograms=histograms, bin_centers=bin_centers, savename=savename, plots_folder=plots_folder)
+        display_bkg(data, background, std_bkg, headers, histograms=histograms, binning=binning, coeff=coeff, savename=savename, plots_folder=plots_folder)
     return n_data_array, n_error_array, headers, background
 
 
-def bkg_mini(data, error, mask, headers, sub_shape=(15,15), display=False, savename=None, plots_folder=""):
+def bkg_mini(data, error, mask, headers, sub_shape=(15,15), subtract_error=True, display=False, savename=None, plots_folder=""):
     """
     Look for sub-image of shape sub_shape that have the smallest integrated
     flux (no source assumption) and define the background on the image by the
@@ -290,6 +436,7 @@ def bkg_mini(data, error, mask, headers, sub_shape=(15,15), display=False, saven
         n_error_array[i] = np.sqrt(n_error_array[i]**2 + error_bkg[i]**2 + err_wav**2 + err_psf**2 + err_flat**2)
         
         #Substract background
+        if subtract_error:
             n_data_array[i][mask] = n_data_array[i][mask] - bkg
             n_data_array[i][np.logical_and(mask,n_data_array[i] <= 0.01*bkg)] = 0.01*bkg
  

src/lib/plots.py

@@ -309,7 +309,7 @@ def polarization_map(Stokes, data_mask=None, rectangle=None, SNRp_cut=3., SNRi_c
     if display.lower() in ['intensity']:
         # If no display selected, show intensity map
         display='i'
-        vmin, vmax = np.min(stkI.data[mask]*convert_flux)/5., np.max(stkI.data[stkI.data > 0.]*convert_flux)
+        vmin, vmax = np.max(np.sqrt(stk_cov.data[0,0][mask])*convert_flux), np.max(stkI.data[stkI.data > 0.]*convert_flux)
         im = ax.imshow(stkI.data*convert_flux, norm=LogNorm(vmin,vmax), aspect='equal', cmap='inferno', alpha=1.)
         cbar = plt.colorbar(im, cax=cbar_ax, label=r"$F_{\lambda}$ [$ergs \cdot cm^{-2} \cdot s^{-1} \cdot \AA^{-1}$]")
         levelsI = np.linspace(vmax*0.01, vmax*0.99, 10)
@@ -320,7 +320,7 @@ def polarization_map(Stokes, data_mask=None, rectangle=None, SNRp_cut=3., SNRi_c
         # Display polarisation flux
         display='pf'
         pf_mask = (stkI.data > 0.) * (pol.data > 0.)
-        vmin, vmax = np.min(stkI.data[mask]*convert_flux)/5., np.max(stkI.data[stkI.data > 0.]*convert_flux)
+        vmin, vmax = np.max(np.sqrt(stk_cov.data[0,0][mask])*convert_flux), np.max(stkI.data[stkI.data > 0.]*convert_flux)
         im = ax.imshow(stkI.data*convert_flux*pol.data, norm=LogNorm(vmin,vmax), aspect='equal', cmap='inferno', alpha=1.)
         cbar = plt.colorbar(im, cax=cbar_ax, label=r"$F_{\lambda} \cdot P$ [$ergs \cdot cm^{-2} \cdot s^{-1} \cdot \AA^{-1}$]")
         levelsPf = np.linspace(vmax*0.01, vmax*0.99, 10)
@@ -1736,21 +1736,17 @@ class pol_map(object):
             self.display_selection = "total_flux"
         if self.display_selection.lower() in ['total_flux']:
             self.data = self.I*self.convert_flux
-            try:
+            vmin, vmax = np.max(np.sqrt(self.IQU_cov[0,0][self.cut])*self.convert_flux), np.max(self.data[self.data > 0.])
-                vmin, vmax = np.min(self.data[self.cut])/5., np.max(self.data[self.data > 0.])
-            except ValueError:
-                vmax = np.max(self.data[self.data > 0.])
-                vmin = vmax*1e-3
             norm = LogNorm(vmin, vmax)
             label = r"$F_{\lambda}$ [$ergs \cdot cm^{-2} \cdot s^{-1} \cdot \AA^{-1}$]"
         elif self.display_selection.lower() in ['pol_flux']:
             self.data = self.I*self.convert_flux*self.P
-            vmin, vmax = np.min(self.I[self.cut]*self.convert_flux)/5., np.max(self.I[self.data > 0.]*self.convert_flux)
+            vmin, vmax = np.max(np.sqrt(self.IQU_cov[0,0][self.cut])*self.convert_flux), np.max(self.I[self.data > 0.]*self.convert_flux)
             norm = LogNorm(vmin, vmax)
             label = r"$F_{\lambda} \cdot P$ [$ergs \cdot cm^{-2} \cdot s^{-1} \cdot \AA^{-1}$]"
         elif self.display_selection.lower() in ['pol_deg']:
             self.data = self.P*100.
-            vmin, vmax = 0., np.max(self.data[self.data > 0.])
+            vmin, vmax = 0., 100. #np.max(self.data[self.data > 0.])
             label = r"$P$ [%]"
         elif self.display_selection.lower() in ['pol_ang']:
             self.data = princ_angle(self.PA)

src/lib/reduction.py

@@ -53,7 +53,7 @@ log.setLevel('ERROR')
 import warnings
 from lib.deconvolve import deconvolve_im, gaussian_psf, gaussian2d, zeropad
 from lib.convex_hull import image_hull, clean_ROI
-from lib.background import bkg_hist, bkg_mini
+from lib.background import bkg_fit, bkg_hist, bkg_mini
 from lib.plots import plot_obs
 from lib.cross_correlation import phase_cross_correlation
 
@@ -409,8 +409,8 @@ def deconvolve_array(data_array, headers, psf='gaussian', FWHM=1., scale='px',
 
 
 def get_error(data_array, headers, error_array=None, data_mask=None,
-            sub_type=None, display=False, savename=None, plots_folder="",
+            sub_type=None, subtract_error=True, display=False, savename=None,
-            return_background=False):
+            plots_folder="", return_background=False):
     """
     Look for sub-image of shape sub_shape that have the smallest integrated
     flux (no source assumption) and define the background on the image by the
@@ -431,10 +431,11 @@ def get_error(data_array, headers, error_array=None, data_mask=None,
         If None, will be initialized with a full true mask.
         Defaults to None.
     sub_type : str or int or tuple, optional
-        If str, statistic rule to be used for the number of bins in counts/s.
+        If 'auto', look for optimal binning and fit intensity histogram with au gaussian.
+        If str or None, statistic rule to be used for the number of bins in counts/s.
         If int, number of bins for the counts/s histogram.
         If tuple, shape of the sub-image to look for. Must be odd.
-        Defaults to "Freedman-Diaconis".
+        Defaults to None.
     display : boolean, optional
         If True, data_array will be displayed with a rectangle around the
         sub-image selected for background computation.
@@ -468,18 +469,26 @@ def get_error(data_array, headers, error_array=None, data_mask=None,
     # Crop out any null edges
     if error_array is None:
         error_array = np.zeros(data_array.shape)
-    n_data_array, n_error_array = deepcopy(data_array), deepcopy(error_array)
+    data, error = deepcopy(data_array), deepcopy(error_array)
     if not data_mask is None:
-        data, error, mask = n_data_array, n_error_array, deepcopy(data_mask)
+        mask = deepcopy(data_mask)
     else:
-        data, error, _ = crop_array(n_data_array, headers, n_error_array, step=5, null_val=0., inside=False)
+        data_c, error_c, _ = crop_array(data, headers, error, step=5, null_val=0., inside=False)
-        mask = np.ones(data[0].shape, dtype=bool)
+        mask_c = np.ones(data_c[0].shape, dtype=bool)
+        for i,(data_ci, error_ci) in enumerate(zip(data_c, error_c)):
+            data[i], error[i] = zeropad(data_ci, data[i].shape), zeropad(error_ci, error[i].shape)
+        mask = zeropad(mask_c, data[0].shape).astype(bool)
     background = np.zeros((data.shape[0]))
     
-    if (sub_type is None) or (type(sub_type)==str):
+    if (sub_type is None):
-        n_data_array, n_error_array, headers, background = bkg_hist(data, error, mask, headers, sub_type=sub_type, display=display, savename=savename, plots_folder=plots_folder)
+        n_data_array, n_error_array, headers, background = bkg_hist(data, error, mask, headers, subtract_error=subtract_error, display=display, savename=savename, plots_folder=plots_folder)
+    elif type(sub_type)==str:
+        if sub_type.lower() in ['auto']:
+            n_data_array, n_error_array, headers, background = bkg_fit(data, error, mask, headers, subtract_error=subtract_error, display=display, savename=savename, plots_folder=plots_folder)
+        else:
+            n_data_array, n_error_array, headers, background = bkg_hist(data, error, mask, headers, sub_type=sub_type, subtract_error=subtract_error, display=display, savename=savename, plots_folder=plots_folder)
     elif type(sub_type)==tuple:
-        n_data_array, n_error_array, headers, background = bkg_mini(data, error, mask, headers, sub_shape=sub_type, display=display, savename=savename, plots_folder=plots_folder)
+        n_data_array, n_error_array, headers, background = bkg_mini(data, error, mask, headers, sub_shape=sub_type, subtract_error=subtract_error, display=display, savename=savename, plots_folder=plots_folder)
     else:
         print("Warning: Invalid subtype.")
 
@@ -674,7 +683,7 @@ def align_data(data_array, headers, error_array=None, background=None,
         raise ValueError("All images in data_array must have same shape as\
             ref_data")
     if (error_array is None) or (background is None):
-        _, error_array, headers, background = get_error_hist(data_array, headers, return_background=True)
+        _, error_array, headers, background = get_error(data_array, headers, sub_type=(10,10), return_background=True)
 
     # Crop out any null edges
     #(ref_data must be cropped as well)