Dotplot

phylofiller/rna.py

@@ -0,0 +1,238 @@
+import pandas as pd
+import numpy as np
+import matplotlib.pyplot as plt
+
+
+def read_dotplot(fp_dotplot, omit_MEA=True):
+    """Read a dot postscript file from Vienna.
+
+    Parameters
+    ----------
+    fp_dotplot : str
+        Filepath to dot.ps file, procuded by e.g. RNAfold
+    omit_MEA : bool
+        If True, only report base pair probabilities, i.e. upper right
+        triangle but NO base pairs used in the Maximum Expected Accurracy
+        secondary structure, i.e. lower left triangle (= lbox)
+
+    Returns
+    -------
+    A tuple of a pandas.DataFrame and a nucleotide sequence as a str.
+    The dataframe has a two level index of type int to indicate start and
+    end positions of all read base pairs and one column calles "probabilities"
+    that holds the actual base pair probabilities, i.e. read data from the ps
+    file CONVERTED from sqrt(prob) to prob.
+                       probability
+        start end
+        1     17      0.177101
+              19      0.172224
+              21      0.277901
+              24      0.084927
+              38      0.212154
+        ...                ...
+        38    46      0.194564
+        39    44      0.130276
+        40    45      0.347719
+        41    45      0.090910
+        42    46      0.103339
+    If omit_MEA == False, the DataFrame holds an additional column "box"
+    flagging each probability as either ubox (uppler right triangle) or
+    lbox (lower left triangle = MEA).
+    """
+    data = None
+    seq = []
+
+    recordseq = False
+    breakNext = False
+    peek = None
+    with open(fp_dotplot, 'r') as f:
+        for lnr, line in enumerate(f.readlines()):
+            if line.startswith(') } def'):
+                recordseq = False
+            if recordseq:
+                seq.append(line.strip().replace('\\', ''))
+            if line.startswith('/sequence { ('):
+                recordseq = True
+            if line.startswith('%start of base pair probability data'):
+                breakNext = True
+                continue
+            if breakNext:
+                peek = line
+                break
+        # rnafold and rnaalifold produce different data blocks:
+        # RNAfold:
+        # %start of base pair probability data
+        # 1 8 0.003375481 ubox
+        # 1 9 0.003326045 ubox
+        #
+        # RNAalifold:
+        # %start of base pair probability data
+        # 0.99 1.00 hsb 1 73 0.999728 ubox
+        # 0.60 1.00 hsb 1 73 0.399728 ubox
+        #
+        # we peek into the first data row and decide on the number of fields
+        # which program might be the source
+        fields = ['start', 'end', 'probability', 'box']  # default to RNAfold
+        if len(peek.strip().split()) > 4:
+            fields = ['field1', 'field2', 'hsb', 'start', 'end', 'probability',
+                      'box']
+
+        data = pd.read_csv(fp_dotplot, sep=" ", skiprows=lnr+1, header=None,
+                           names=fields).iloc[:-3]
+        # convert sqrt(p(i,j)) back to p(i,j)
+        data['probability'] = data['probability'].apply(lambda x: np.sqrt(x))
+
+        for field in ['start', 'end']:
+            data[field] = data[field].astype(int)
+        for field in ['probability']:
+            data[field] = data[field].astype(float)
+
+        if omit_MEA:
+            data = data[data['box'] != 'lbox']
+            del data['box']
+
+    return data.set_index(['start', 'end']), ''.join(seq)
+
+
+def dotPlot(bp_ref, seq_ref, bp_mut=None, seq_mut=None, plotsize=10, title="",
+            drawSequence=True, color_ref='darkgreen', color_mut='darkred',
+            color_both='yellow'):
+    """Produces an RNA 'dot-plot' to visualize base-pair probabilities.
+
+    Parameters
+    ----------
+    bp_ref : pandas.DataFrame
+        Base pair probabilities for a reference folding space.
+        The datatype is a pandas DataFrame with a two level index of type
+        int that address positions of the base pair and one column that
+        holds base pair probabilities, e.g.
+
+                   probability
+        start end
+        1     17      0.177101
+              19      0.172224
+              21      0.277901
+              24      0.084927
+              38      0.212154
+        ...                ...
+        38    46      0.194564
+        39    44      0.130276
+        40    45      0.347719
+        41    45      0.090910
+        42    46      0.103339
+    seq_ref : str
+        The nucleotide sequence of the RNA molecule.
+        (It is used to determine the size of the dot-plot.)
+    bp_mut : pandas.DataFrame
+        Base pair probabilities of an alternative folding space,
+        e.g. a mutated RNA molecule. Datatype is the same as in
+        bp_ref.
+    seq_mut : str
+        The nucleotide sequence of a mutated RNA molecule.
+    plotsize : int
+        The relative size of the figure, which also depends on the
+        seq_ref length.
+    title : str
+        A title for the dot-plot.
+    drawSequence : bool
+        seq_ref and/or seq_mut won't we used as tick labels if set
+        to False.
+    color_ref : str
+        The color to plot base-pair probabilities for the reference
+        folding space.
+    color_mut : str
+        The color to plot base-pair probabilities for the mutated
+        folding space.
+    color_both : str
+        The color to plot base-pair probabilities that overlap between
+        the reference and the mutated folding space.
+
+    Returns
+    -------
+    plt.figure
+    """
+    length = len(seq_ref)
+    plotsize = 0.15 * length
+
+    fig, ax = plt.subplots(figsize=(plotsize, plotsize))
+
+    # grid at every 10th base
+    for pos in range(10, length, 10):
+        ax.axvline(x=pos, color='gray', linewidth=0.5, zorder=-5.0)
+        ax.axhline(y=pos, color='gray', linewidth=0.5, zorder=-5.0)
+
+    # diagonal line
+    ax.plot([-0.5, length], [-0.5, length], color='black', linewidth=0.5)
+
+    # plot overlay of two base pair probability sets
+    for ((start, end), probs) in pd.concat(
+            [bp_ref, bp_mut], axis=1).fillna(0).iterrows():
+        bpprobA = probs.iloc[0]
+        bpprobB = 0
+        if probs.shape[0] == 2:
+            bpprobB = probs.iloc[1]
+
+        # scale basepair probability with square area -> take square root
+        # (same as in Vienna)
+        (sizeA, sizeB) = map(lambda x: x**2, (bpprobA, bpprobB))
+
+        def _getCoords(start, end, size):
+            return start - (size / 2) - 1, end - (size / 2) - 1
+        size_larger, (x_larger, y_larger) = sizeA, _getCoords(
+            start, end, sizeA)
+        size_smaller, (x_smaller, y_smaller) = sizeB, _getCoords(
+            start, end, sizeB)
+        color = color_ref
+        if bpprobB > bpprobA:
+            size_larger, (x_larger, y_larger), \
+                size_smaller, (x_smaller, y_smaller) = \
+                size_smaller, (x_smaller, y_smaller), \
+                size_larger, (x_larger, y_larger)
+            color = color_mut
+        ax.add_patch(plt.Rectangle((y_larger, x_larger),
+                                   size_larger, size_larger, color=color))
+        if size_smaller > 0:
+            ax.add_patch(plt.Rectangle((y_smaller, x_smaller),
+                                       size_smaller, size_smaller,
+                                       color=color_both))
+
+    ax.set_xlim((-0.5, length - 0.5))
+    ax.set_ylim((-0.5, length - 0.5))
+
+    if seq_mut is None:
+        seq_mut = seq_ref
+    top_x = list(map(lambda x: '\n'.join(x) if x[0] != x[1] else "\n" + x[0],
+                 zip(seq_mut, seq_ref)))
+    bottom_x = list(
+        map(lambda x: '\n'.join(x) if x[0] != x[1] else x[0] + "\n",
+            zip(seq_ref, seq_mut)))
+    left_y = list(map(lambda x: ' '.join(x) if x[0] != x[1] else x[0],
+                  zip(seq_mut, seq_ref)))
+    right_y = list(map(lambda x: ' '.join(x) if x[0] != x[1] else x[0],
+                   zip(seq_ref, seq_mut)))
+    # sequence as tick labels at all four corners
+    if drawSequence:
+        ax.set_xticks(range(0, length), )
+        ax.set_xticklabels(bottom_x, fontsize=6)
+        ax.tick_params(axis=u'both', which=u'both', length=0)
+
+        ax.set_yticks(ax.get_xticks())
+        ax.set_yticklabels(left_y, fontsize=6, ha="right")
+
+        ax2 = ax.twiny()
+        ax2.set_xlim(ax.get_xlim())
+        ax2.set_xticks(ax.get_xticks())
+        ax2.set_xticklabels(top_x, fontsize=6)
+        ax2.tick_params(axis=u'both', which=u'both', length=0)
+
+        ax3 = ax.twinx()
+        ax3.set_ylim(ax.get_ylim())
+        ax3.set_yticks(ax.get_xticks())
+        ax3.set_yticklabels(reversed(right_y), fontsize=6, ha='left')
+        ax3.tick_params(axis=u'both', which=u'both', length=0)
+
+    ax.invert_yaxis()
+
+    ax.set_title(title, fontsize=30)
+
+    return fig