How to plot a very simple bar chart Python Matplotlib using input txt file

Question

I use Python 2 7 and matplotlib  I have a   txt data file    0 14-11-2003 1 15-03-1999 12 04-12-2012 33 09-05-2007 44 16-08-1998 55 25-07-2001 76 31-12-2011 87 25-06-1993 118 16-02-1995 119 10-02-1981 145 03-05-2014   first column of my file  numbers  should be on axis Y in my bar chart  and the second column from my file  dates  should be on axis OX in my histogram  I only know how to read the file   OX      OY       try       with open  data txt    r   as openedFile           for line in openedFile               tab   line split               OY append int tab 0                OX append str tab 1    except IOError       print  IOError      I did read a matplotlib docs but it still doesn t help me  I would also like to add dates I read to my bar chart  to make it look like    Could someone please help me

User · Answer

This code will do what you re looking for  It s based on examples found here and here   The autofmt xdate   call is particularly useful for making the x-axis labels readable   import numpy as np from matplotlib import pyplot as plt  fig   plt figure    width    35 ind   np arange len OY   plt bar ind  OY  width width  plt xticks ind   width   2  OX   fig autofmt xdate    plt savefig  figure pdf

User · Answer

First  what you are looking for is a column or bar diagram  not really a histogram  A histogram is made from a frequency distribution of a continuous variable that is separated into bins  Here you have a column against separate labels   To make a bar diagram with matplotlib  use the matplotlib pyplot bar   method  Have a look at this page of the matplotlib documentation that explains very well with examples and source code how to do it   If it is possible though  I would just suggest that for a simple task like this if you could avoid writing code that would be better  If you have any spreadsheet program this should be a piece of cake because that s exactly what they are for  and you won t have to  reinvent the wheel   The following is the plot of your data in Excel     I just copied your data from the question  used the text import wizard to put it in two columns  then I inserted a column diagram

User · Answer

You re talking about histograms  but this doesn t quite make sense  Histograms and bar charts are different things  An histogram would be a bar chart representing the sum of values per year  for example  Here  you just seem to be after bars   Here is a complete example from your data that shows a bar of for each required value at each date   import pylab as pl import datetime  data      0 14-11-2003 1 15-03-1999 12 04-12-2012 33 09-05-2007 44 16-08-1998 55 25-07-2001 76 31-12-2011 87 25-06-1993 118 16-02-1995 119 10-02-1981 145 03-05-2014     values      dates       for line in data split   n        x  y   line split       values append int x       dates append datetime datetime strptime y    d- m- Y   date     fig   pl figure   ax   pl subplot 111  ax bar dates  values  width 100  ax xaxis date     You need to parse the date with strptime and set the x-axis to use dates  as described in this answer    If you re not interested in having the x-axis show a linear time scale  but just want bars with labels  you can do this instead   fig   pl figure   ax   pl subplot 111  ax bar range len dates    values    EDIT  Following comments  for all the ticks  and for them to be centred  pass the range to set ticks  and move them by half the bar width    fig   pl figure   ax   pl subplot 111  width 0 8 ax bar range len dates    values  width width  ax set xticks np arange len dates     width 2  ax set xticklabels dates  rotation 90

[python] How to plot a very simple bar chart (Python, Matplotlib) using input *.txt file?

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