文章MSM_metagenomics（五）：共现分析

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介绍

本教程是使用一个Python脚本来分析多种微生物（即strains, species, genus等）的共现模式。

数据

大家通过以下链接下载数据：

• 百度网盘链接：https://pan.baidu.com/s/1f1SyyvRfpNVO3sLYEblz1A
• 提取码: 请关注WX公zhong号_生信学习者_后台发送 复现msm 获取提取码

Python packages required

• pandas >= 1.3.5
• matplotlib >= 3.5.0
• seaborn >= 0.11.2

Co-presence pattern analysis

使用step_curve_drawer.py 做共线性分析

• 代码

#!/usr/bin/env python

"""
NAME: step_curve_drawer.py
DESCRIPTION: This script is to analyze the co-prsense of multiple species in different categories,
             by drawing step curves.
"""

import pandas as pd
import seaborn as sns
import matplotlib.pyplot as plt
import sys
import argparse
import textwrap

def read_args(args):
    # This function is to parse arguments

    parser = argparse.ArgumentParser(formatter_class=argparse.RawDescriptionHelpFormatter,
                                    description = textwrap.dedent('''\
                                     This program is to do draw step curves to analyze co-presense of multiple species in different groups.
                                     '''),
                                    epilog = textwrap.dedent('''\
                                    examples:step_curve_drawer.py --abundance_table <abundance_table_w_md.tsv> --variable <variable_name> --species_number <nr_sps> --output <output.svg>
                                    '''))
    parser.add_argument('--abundance_table',
                        nargs = '?',
                        help = 'Input the MetaPhlAn4 abundance table which contains only a group of species one wants to analyze their co-presense state, with metadata being wedged.',
                        type = str,
                        default = None)

    parser.add_argument('--variable',
                        nargs = '?',
                        help = 'Specify the header of the variable in the metadata table you want to assess. For example, \
                        [Diet] variable columns has three categries - [vegan]/[Flexitarian]/[Omnivore].',
                        type = str,
                        default = None)

    parser.add_argument('--minimum_abundance',
                        nargs = '?',
                        help = 'Specify the minimum abundance used for determining presense. note: [0, 100] and [0.0] by default',
                        type = float,
                        default = 0.0)

    parser.add_argument('--species_number',
                        nargs = '?',
                        help = 'Specify the total number of multiple species in the analysis.',
                        type = int)


    parser.add_argument('--output',
                        nargs = '?',
                        help = 'Specify the output figure name.',
                        type = str,
                        default = None)
    parser.add_argument('--palette',
                        nargs = '?',
                        help = 'Input a tab-delimited mapping file where values are group names and keys are color codes.',
                        type = str,
                        default = None)

    return vars(parser.parse_args())

class PandasDealer:
    """
    This is an object for dealing pandas dataframe.
    """

    def __init__(self, df_):

        self.df_ = df_

    def read_csv(self):
        # Ths fucntion will read tab-delimitted file into a pandas dataframe.

        return pd.read_csv(self.df_, sep = '\t', index_col = False, low_memory=False)

    def rotate_df(self):
        # this function is to rotate the metaphlan-style table into tidy dataframe to ease searching work,

        df_ = self.read_csv()
        df_rows_lists = df_.values.tolist()
        rotated_df_dict = {df_.columns[0]: df_.columns[1:]}
        for i in df_rows_lists:
            rotated_df_dict[i[0]] = i[1:]

        rotated_df = pd.DataFrame.from_dict(rotated_df_dict)
        
        return rotated_df

class CopEstimator:

    def __init__(self, sub_df_md):
        self.sub_df_md = sub_df_md # sub_df_md: a subset of dataframe which contains only a group of species one wants to do co-presence analysis.

    def make_copresense_df(self, factor, total_species_nr, threshold = 0.0):
        # factor: the factor you want to assess the category percentage.
        # total_species_nr: specify the total number of species you want to do co-presense analysis.


        rotated_df = PandasDealer(self.sub_df_md)
        rotated_df = rotated_df.rotate_df()
        cols = rotated_df.columns[-total_species_nr: ].to_list() 
        categories = list(set(rotated_df[factor].to_list()))
        

        copresense = []
        cate_name = []
        ratios = []
        for c in categories:
            sub_df = rotated_df[rotated_df[factor] == c]
            species_group_df = sub_df[cols]
            species_group_df = species_group_df.apply(pd.to_numeric)
            species_group_df['total'] = species_group_df[cols].gt(threshold).sum(axis=1)
            for i in range(1, total_species_nr + 1):
                ratio = count_non_zero_rows(species_group_df, i)
                copresense.append(i)
                cate_name.append(c)
                ratios.append(ratio)

        return pd.DataFrame.from_dict({"copresense": copresense,
                                        factor: cate_name,
                                        "percentage": ratios})

def count_non_zero_rows(df_, nr):
    total_rows = len(df_.index)
    
    sub_df = df_[df_['total'] >= nr]
    ratio = len(sub_df.index)/total_rows

    return ratio
    

class VisualTools:
    def __init__(self, processed_df, factor):
        self.processed_df = processed_df
        self.factor = factor

    def step_curves(self, opt_name, palette = None):
        categories = list(set(self.processed_df[self.factor].to_list()))
        if palette:
            palette_dict = {i.rstrip().split('\t')[0]: i.rstrip().split('\t')[1] for i in open(palette).readlines()}
            for c in categories:
                sub_df = self.processed_df[self.processed_df[self.factor] == c]
                plt.step(sub_df["percentage"]*100, sub_df["copresense"], label = c, color = palette_dict[c])
        else:
            for c in categories:
                sub_df = self.processed_df[self.processed_df[self.factor] == c]
                plt.step(sub_df["percentage"]*100, sub_df["copresense"], label = c)

        plt.title("Number of species in an individual if present")
        plt.xlabel("Percentage")
        plt.ylabel("Co-presense")
        plt.legend(title = self.factor)
        plt.savefig(opt_name, bbox_inches = "tight")


if __name__ == "__main__":

    pars = read_args(sys.argv)
    cop_obj = CopEstimator(pars['abundance_table'])
    p_df = cop_obj.make_copresense_df(pars['variable'], pars['species_number'], pars['minimum_abundance'])
    vis_obj = VisualTools(p_df, pars['variable'])
    vis_obj.step_curves(pars['output'], palette = pars['palette'])

• 用法

usage: step_curve_drawer.py [-h] [--abundance_table [ABUNDANCE_TABLE]] [--variable [VARIABLE]] [--minimum_abundance [MINIMUM_ABUNDANCE]] [--species_number [SPECIES_NUMBER]] [--output [OUTPUT]]
                            [--palette [PALETTE]]

This program is to do draw step curves to analyze co-presense of multiple species in different groups.

optional arguments:
  -h, --help            show this help message and exit
  --abundance_table [ABUNDANCE_TABLE]
                        Input the MetaPhlAn4 abundance table which contains only a group of species one wants to analyze their co-presense state, with metadata being wedged.
  --variable [VARIABLE]
                        Specify the header of the variable in the metadata table you want to assess. For example, [Diet] variable columns has three categries - [vegan]/[Flexitarian]/[Omnivore].
  --minimum_abundance [MINIMUM_ABUNDANCE]
                        Specify the minimum abundance used for determining presense. note: [0, 100] and [0.0] by default
  --species_number [SPECIES_NUMBER]
                        Specify the total number of multiple species in the analysis.
  --output [OUTPUT]     Specify the output figure name.
  --palette [PALETTE]   Input a tab-delimited mapping file where values are group names and keys are color codes.

examples:

python step_curve_drawer.py --abundance_table <abundance_table_w_md.tsv> --variable <variable_name> --species_number <nr_sps> --output <output.svg>

为了演示step_curve_drawer.py的使用，我们将绘制基于metaphlan相对丰度表特定于Segatalla copri （之前称为Prevotella copri ）的八个谱系：./data/mpa4_pcopri_abundances_md.tsv的共现模式，这些数据来自MSM 和Non-MSM 人群。MSM 和Non-MSM 样本将使用自定义颜色进行标记，颜色分配来自一个颜色映射文件color map file: ./data/copresence_color_map.tsv。

python step_curve_drawer.py \
  --abundance_table mpa_pcopri_abundances_md.tsv \
  --variable sexual_orientation \
  --species_number 8 \
  --palette copresence_color_map.tsv \
  --output copresence_plot.png