Matplotlib Histogram not equal data sets - python

I would like to create a histogram that will use the following. I know this is because lengths of my menMeans and womenMeans are not equal. If I was not hard coding the list, and possible wanted to add some more list later to provide more bars how would I do this? What is the best way to scale the graph with knowing that the bars will not always have like sets of values.
import numpy as np
import matplotlib.pyplot as plt
fig = plt.figure()
ax = fig.add_subplot(111)
## the data
N = 5
menMeans = [18, 35, 30, 35, 27] ### len=5
womenMeans = [25, 32, 34, 20, 25,42] ### len =6
## necessary variables
ind = np.arange(N) # the x locations for the groups
width = 0.35 # the width of the bars
## the bars
rects1 = ax.bar(ind, menMeans, width,
color='black')
rects2 = ax.bar(ind+width, womenMeans, width,
color='red')
# axes and labels
ax.set_xlim(-width,len(ind)+width)
ax.set_ylim(0,45)
ax.set_ylabel('Scores')
ax.set_title('Scores by group and gender')
xTickMarks = ['Group'+str(i) for i in range(1,7)]
ax.set_xticks(ind+width)
xtickNames = ax.set_xticklabels(xTickMarks)
plt.setp(xtickNames, rotation=45, fontsize=10)
## add a legend
ax.legend( (rects1[0], rects2[0]), ('Men', 'Women') )
plt.show()
The error I get is:
Traceback (most recent call last):
File "C:\Python27\test_3.py", line 22, in <module>
color='red')
File "C:\Python27\lib\site-packages\matplotlib\axes.py", line 4999, in bar
nbars)
AssertionError: incompatible sizes: argument 'height' must be length 5 or scalar


I think the easiest way to address this would be to add one or more zero means to the men's list until it's the same length as the other one. The extra zero means don't change the appearance of the graph - it just looks like the bar is absent:
Here's a simple general function to do that:
def equalizeLists(*lists):
maxLen = max([len(list) for list in lists])
for list in lists:
list = list.extend([0]*(maxLen - len(list)))
return maxLen
This will equalize the lengths of two or more lists automatically by adding zeros to the ends of the shorter ones. You could insert it into your code like so:
## the data
menMeans = [18, 35, 30, 35, 27]
womenMeans = [25, 32, 34, 20, 25,42]
N = equalizeLists(menMeans, womenMeans)

Related

How to create a figure of subplots of grouped bar charts in python

I want to combine multiple grouped bar charts into one figure, as the image below shows.
grouped bar charts in a single figure
import matplotlib
import matplotlib.pyplot as plt
import numpy as np
labels = ['G1', 'G2', 'G3']
yesterday_test1_mean = [20, 12, 23]
yesterday_test2_mean = [21, 14, 25]
today_test1_mean = [18, 10, 12]
today_test2_mean = [13, 13, 9]
Firstly I created each grouped bar chart by plt.subplots()
x = np.arange(len(labels))
width = 0.3
fig1, ax = plt.subplots()
rects1 = ax.bar(x-width/2, yesterday_test1_mean, width)
rects2 = ax.bar(x+width/2, yesterday_test2_mean, width)
fig2, ax = plt.subplots()
rects3 = ax.bar(x-width/2, today_test1_mean, width)
rects4 = ax.bar(x+width/2, today_test2_mean, width)
Then, I used add_subplot in an attempt to treat fig1 and fig2 as new axes in a new figure.
fig_all = plt.figure()
fig1 = fig_all.add_subplot(1,2,1)
fig2 = fig_all.add_subplot(1,2,2)
fig_all.tight_layout()
plt.show()
But it didn't work. How can I combined several grouped bar charts into a single figure?
Thanks in advance.

Well, I tried something. Here's a rough result. Only thing I changed is that rather using axes, I am just using subplot as I learned over time. So with fig and axes as output, there must be a way too. But this is all I've ever used. I've not added the legend and title yet, but I guess you can try it on your own too.
Here's the code with just small change:
import matplotlib.pyplot as plt
import numpy as np
labels = ['G1', 'G2', 'G3']
yesterday_test1_mean = [20, 12, 23]
yesterday_test2_mean = [21, 14, 25]
today_test1_mean = [18, 10, 12]
today_test2_mean = [13, 13, 9]
x = np.arange(len(labels))
width = 0.3
plt.figure(figsize=(12,5))
plt.subplot(121)
plt.bar(x-width/2, yesterday_test1_mean, width)
plt.bar(x+width/2, yesterday_test2_mean, width)
plt.subplot(122)
plt.bar(x-width/2, today_test1_mean, width)
plt.bar(x+width/2, today_test2_mean, width)
plt.show()
And here's your initial result:
While you see the result and try some stuff on your own, let me try to add the labels and legend to it as well as you've provided in the sample image.
Edit: The final output
So here it is, the exact thing you're looking for:
Code:
import matplotlib.pyplot as plt
import numpy as np
labels = ['G1', 'G2', 'G3']
yesterday_test1_mean = [20, 12, 23]
yesterday_test2_mean = [21, 14, 25]
today_test1_mean = [18, 10, 12]
today_test2_mean = [13, 13, 9]
x = np.arange(len(labels))
width = 0.3
plt.figure(figsize=(12,5))
plt.subplot(121)
plt.title('Yesterday', fontsize=18)
plt.bar(x-width/2, yesterday_test1_mean, width, label='test1', hatch='//', color=np.array((199, 66, 92))/255)
plt.bar(x+width/2, yesterday_test2_mean, width, label='test2', color=np.array((240, 140, 58))/255)
plt.xticks([0,1,2], labels, fontsize=15)
plt.subplot(122)
plt.title('Today', fontsize=18)
plt.bar(x-width/2, today_test1_mean, width, hatch='//', color=np.array((199, 66, 92))/255)
plt.bar(x+width/2, today_test2_mean, width, color=np.array((240, 140, 58))/255)
plt.xticks([0,1,2], labels, fontsize=15)
plt.figlegend(loc='upper right', ncol=1, labelspacing=0.5, fontsize=14, bbox_to_anchor=(1.11, 0.9))
plt.tight_layout(w_pad=6)
plt.show()

There is two method for doing subplots that you might try to combine accidentally: plt.subplot and plt.subplots.
Here is example how you can use plt.subplots to create two bar charts.
import numpy as np
import matplotlib.pyplot as plt
labels = ['G1', 'G2', 'G3']
yesterday_test1_mean = [20, 12, 23]
yesterday_test2_mean = [21, 14, 25]
today_test1_mean = [18, 10, 12]
today_test2_mean = [13, 13, 9]
x = np.arange(len(labels))
width = 0.3
fig, (ax1, ax2) = plt.subplots(1, 2)
ax1.bar(x-width/2, yesterday_test1_mean, width)
ax1.bar(x+width/2, yesterday_test2_mean, width)
ax2.bar(x-width/2, today_test1_mean, width)
ax2.bar(x+width/2, today_test2_mean, width)
plt.show()
There is only little changes on your code. You can add labels with:
ax1.set_title('Yesterday')
ax2.set_title('Today')
ax1.set_xticks(x)
ax1.set_xticklabels(labels)
ax2.set_xticks(x)
ax2.set_xticklabels(labels)

Single stacked bar chart with custom gradient coloring

Here's what I came up with by plotting thick line segments.
The coloration is blue, with varying alpha, 0 < alpha < 1.
My workaround doens't work as I'd like because I don't have a legend (I want a legend that shows a gradient of the blue at varying alpha).
Additionally, I've found that matplotlib scales funny. There should be no overlap of the bars, but if I adjust the window size, the gap between the line segments will change.This is the same figure as the earlier one, just after I've resized the figure window with my mouse.
I'm not sure if there's a better way to go about accomplishing this, or if there's a different package I can use.
Here's the snippet of code that I'm using.
import matplotlib.pyplot as plt
x1 =[0, 19, 39, 46, 60, 79]
x2 = [19, 39, 46, 60, 79, 90]
alpha_list = [-0.8402, -0.6652, 0.0, -0.5106, -0.8074, 0.0]
plt.figure()
for idx,x in enumerate(x1):
plt.plot([x1[idx],x2[idx]],[0,0],color = 'blue',alpha=alpha_list[idx],linewidth =20)
plt.show()

I suppose alpha is just a workaround for using different shades of blue? In that case the Blues colormap can be used instead.
Several lines can be plotted using a LineCollection.
import numpy as np
import matplotlib.pyplot as plt
from matplotlib.collections import LineCollection
x1 =[0, 19, 39, 46, 60, 79]
x2 = [19, 39, 46, 60, 79, 90]
alpha_list = [-0.8402, -0.6652, 0.0, -0.5106, -0.8074, 0.0]
verts = np.dstack((np.c_[x1, x2], np.zeros((len(x1), 2))))
fig, ax = plt.subplots()
lc = LineCollection(verts, linewidth=40, cmap="Blues_r", array=np.array(alpha_list))
ax.add_collection(lc)
ax.autoscale()
ax.set_ylim(-1,1)
fig.colorbar(lc)
plt.show()

I think a workaround would be to use plt.barh. Here is an example using normalized color maps. Each color gets converted to RGBA before it can be passed to plt.barh.
import matplotlib.pyplot as plt
from matplotlib import colors
import matplotlib.cm as cmx
x1 =[0, 19, 39, 46, 60, 79]
x2 = [19, 39, 46, 60, 79, 90]
values = range(len(x1))
jet = cm = plt.get_cmap('jet')
cNorm = colors.Normalize(vmin=0, vmax=values[-1])
scalarMap = cmx.ScalarMappable(norm=cNorm, cmap=jet)
fig, ax = plt.subplots()
for idx, x, y in zip(values,x1, x2):
colorVal = scalarMap.to_rgba(values[idx])
start = x
end = y
width=end-start
ax.barh(y = 0, width = width, left=start, height = 0.1, label = str(idx), color=colorVal)
ax.set_ylim(-.5,0.5)
ax.legend()
which returns:
If you really want to just change the alpha transparency of a single color, you would just have to input alpha_list[idx] for the last element to the RGBA tuple colorVal. For some reason, RGBA did not like negative alpha values, so notice I changed them all to positive
fig, ax = plt.subplots()
alpha_list = [0.8402, 0.6652, 0.01, 0.5106, 0.8074, 0.0]
for idx, x, y in zip(values,x1, x2):
colorVal = (0.0, 0.3, 1.0, alpha_list[idx])
start = x
end = y
width=end-start
ax.barh(y = 0, width = width, left=start, height = 0.1, label = str(idx), color=colorVal)
ax.set_ylim(-.5,0.5)
ax.legend()

Plot a histogram using Python with manual bins

I am trying to plot a histogram using the matplotlib.hist() function.
Below code is not getting the correct histogram
X axis is the years (age), X axis I want to have 0 20, 25, 30, 35, 40, 45, 50, 55
Y axis is the probability
Someone can help me to get the correct histogram ?
import matplotlib.pyplot as plt
list_age = ['26','28','26','36','38','31','22','31','25','30','37','27','27','29','27','21','27','38','31','41','28','31','28','33','26','39','37','24','31','34','39','33','22', '30','24','29','28','34','27','28','26','26','25','40','24','37','24','28','26','29','26','31','23','31','36','32','25','31','25','33','36','27','28',
'25','27','39','36','30','31','34','23','31','32','31','33','32','39','35','35','22','34','25','35','35','41','20','21','35','32','30','22','21','23','33','25','30','24','39','24','27','22','33','30','27','30','23','29','30','22','31','29','31','24','29','25','24','26','29','31','24','32','21','25','29','30']
list_age.sort()
bins = 55
plt.hist(list_age, bins, facecolor='g')
plt.xlabel('Years')
plt.ylabel('Probability')
plt.grid(True)
plt.show()

You need to convert your list_age to a list of integers first (instead of a list of strings).
Then, simply use the options density (or normed) to display probability and xticks to change the ticks for the x-axis.
import matplotlib.pyplot as plt
list_age = ['26','28','26','36','38','31','22','31','25','30','37','27','27','29','27','21','27','38','31','41','28','31','28','33','26','39','37','24','31','34','39','33','22', '30','24','29','28','34','27','28','26','26','25','40','24','37','24','28','26','29','26','31','23','31','36','32','25','31','25','33','36','27','28',
'25','27','39','36','30','31','34','23','31','32','31','33','32','39','35','35','22','34','25','35','35','41','20','21','35','32','30','22','21','23','33','25','30','24','39','24','27','22','33','30','27','30','23','29','30','22','31','29','31','24','29','25','24','26','29','31','24','32','21','25','29','30']
list_age = [ int(i) for i in list_age ]
bins = len(set(list_age))
plt.hist(list_age, bins = bins, density = True, facecolor = "g") # Replace density by normed if older version of matplotlib
plt.xticks(range(0, 55, 5))
plt.xlabel('Years')
plt.ylabel('Probability')
plt.grid(True)
plt.show()
If you want to display the bars at specific bins, simply define bins at their coordinates:
plt.hist(list_age, bins = [ 0, 20, 25, 30, 35, 40, 45, 50, 55 ], density = True, facecolor = "g")

How do I plot stacked histograms side by side in matplotlib?

I'm looking to plot two side-by-side stacked histograms (similar to the example image below) in matplotlib.
I've tried several variations on
bins = np.arange(10)
a1,b1,c1 =plt.hist([arr1,arr2,arr3],bins,stacked=True)
a2,b2,c2 =plt.hist([arr4,arr5,arr6],bins,stacked=True)
But can't seem to avoid getting the second plot to directly overlay the first.
Any ideas on how this could be resolved?

The picture shows a bar chart and not a histogram. I am pointing this out, not only because I am an obnoxious pedant, but also because I believe it could help you find the right tool :-)
Indeed, for your purpose plt.bar is probably a better pick than plt.hist.
Based on Scironic's suggestion, I modified this demonstration example to make stacked bars, like the ones on your figure.
Adding an offset to the position index (first argument in plt.bar()) is what prevents the bars from overlapping each other.
import numpy as np
import matplotlib.pyplot as plt
N = 5
men1 = (130, 90, 70, 64, 55)
men2 = (120, 85, 62, 50, 53)
men3 = (100, 70, 60, 45, 50)
ind = np.arange(N) + .15 # the x locations for the groups
width = 0.35 # the width of the bars
fig, ax = plt.subplots()
rects1 = ax.bar(ind, men1, width, color='g')
rects2 = ax.bar(ind, men2, width, color='r')
rects3 = ax.bar(ind, men3, width, color='b')
women4 = (140, 90, 78, 65, 50)
women5 = (130, 80, 70, 60, 45)
women6 = (120, 60, 60, 55, 44)
xtra_space = 0.05
rects2 = ax.bar(ind + width + xtra_space , women1, width, color='orange')
rects2 = ax.bar(ind + width + xtra_space, women2, width, color='cyan')
rects2 = ax.bar(ind + width + xtra_space, women3, width, color='purple')
# add some text for labels, title and axes ticks
ax.set_ylabel('Population, millions')
ax.set_title('Population: Age Structure')
ax.set_xticks(ind+width+xtra_space)
ax.set_xticklabels( ('USA', 'Brazil', 'Russia', 'Japan', 'Mexico') )
plt.show()

How to plot bar graphs with same X coordinates side by side ('dodged')

import matplotlib.pyplot as plt
gridnumber = range(1,4)
b1 = plt.bar(gridnumber, [0.2, 0.3, 0.1], width=0.4,
label="Bar 1", align="center")
b2 = plt.bar(gridnumber, [0.3, 0.2, 0.2], color="red", width=0.4,
label="Bar 2", align="center")
plt.ylim([0,0.5])
plt.xlim([0,4])
plt.xticks(gridnumber)
plt.legend()
plt.show()
Currently b1 and b2 overlap each other. How do I plot them separately like so:

There is an example in the matplotlib site. Basically, you just shift the x values by width. Here is the relevant bit:
import numpy as np
import matplotlib.pyplot as plt
N = 5
menMeans = (20, 35, 30, 35, 27)
menStd = (2, 3, 4, 1, 2)
ind = np.arange(N) # the x locations for the groups
width = 0.35 # the width of the bars
fig = plt.figure()
ax = fig.add_subplot(111)
rects1 = ax.bar(ind, menMeans, width, color='royalblue', yerr=menStd)
womenMeans = (25, 32, 34, 20, 25)
womenStd = (3, 5, 2, 3, 3)
rects2 = ax.bar(ind+width, womenMeans, width, color='seagreen', yerr=womenStd)
# add some
ax.set_ylabel('Scores')
ax.set_title('Scores by group and gender')
ax.set_xticks(ind + width / 2)
ax.set_xticklabels( ('G1', 'G2', 'G3', 'G4', 'G5') )
ax.legend( (rects1[0], rects2[0]), ('Men', 'Women') )
plt.show()

Below answer will explain each and every line of code in the simplest manner possible:
# Numbers of pairs of bars you want
N = 3
# Data on X-axis
# Specify the values of blue bars (height)
blue_bar = (23, 25, 17)
# Specify the values of orange bars (height)
orange_bar = (19, 18, 14)
# Position of bars on x-axis
ind = np.arange(N)
# Figure size
plt.figure(figsize=(10,5))
# Width of a bar
width = 0.3
# Plotting
plt.bar(ind, blue_bar , width, label='Blue bar label')
plt.bar(ind + width, orange_bar, width, label='Orange bar label')
plt.xlabel('Here goes x-axis label')
plt.ylabel('Here goes y-axis label')
plt.title('Here goes title of the plot')
# xticks()
# First argument - A list of positions at which ticks should be placed
# Second argument - A list of labels to place at the given locations
plt.xticks(ind + width / 2, ('Xtick1', 'Xtick3', 'Xtick3'))
# Finding the best position for legends and putting it
plt.legend(loc='best')
plt.show()

Sometimes could be tricky to find the right bar width. I usually use this np.diff to find the right dimension.
import numpy as np
import matplotlib.pyplot as plt
#The data
womenMeans = (25, 32, 34, 20, 25)
menMeans = (20, 35, 30, 35, 27)
indices = [5.5,6,7,8.5,8.9]
#Calculate optimal width
width = np.min(np.diff(indices))/3
fig = plt.figure()
ax = fig.add_subplot(111)
# matplotlib 3.0 you have to use align
ax.bar(indices-width,womenMeans,width,color='b',label='-Ymin',align='edge')
ax.bar(indices,menMeans,width,color='r',label='Ymax',align='edge')
ax.set_xlabel('Test histogram')
plt.show()
# matplotlib 2.0 (you could avoid using align)
# ax.bar(indices-width,womenMeans,width,color='b',label='-Ymin')
# ax.bar(indices,menMeans,width,color='r',label='Ymax')
This is the result:
What if my indices on my x axis are nominal values like names:
#
import numpy as np
import matplotlib.pyplot as plt
# The data
womenMeans = (25, 32, 34, 20, 25)
menMeans = (20, 35, 30, 35, 27)
indices = range(len(womenMeans))
names = ['Asian','European','North Amercian','African','Austrailian','Martian']
# Calculate optimal width
width = np.min(np.diff(indices))/3.
fig = plt.figure()
ax = fig.add_subplot(111)
ax.bar(indices-width/2.,womenMeans,width,color='b',label='-Ymin')
ax.bar(indices+width/2.,menMeans,width,color='r',label='Ymax')
#tiks = ax.get_xticks().tolist()
ax.axes.set_xticklabels(names)
ax.set_xlabel('Test histogram')
plt.show()

Here are two examples of creating a side-by-side bar chart when you have more than two "categories" in a group.
Manual Method
Manually set the position and width of each bar.
import numpy as np
import matplotlib.pyplot as plt
from matplotlib import ticker
coins = ['penny', 'nickle', 'dime', 'quarter']
worth = np.array([.01, .05, .10, .25])
# Coin values times *n* coins
# This controls how many bars we get in each group
values = [worth*i for i in range(1,6)]
n = len(values) # Number of bars to plot
w = .15 # With of each column
x = np.arange(0, len(coins)) # Center position of group on x axis
for i, value in enumerate(values):
position = x + (w*(1-n)/2) + i*w
plt.bar(position, value, width=w, label=f'{i+1}x')
plt.xticks(x, coins);
plt.ylabel('Monetary Value')
plt.gca().yaxis.set_major_formatter(ticker.FormatStrFormatter('$%.2f'))
plt.legend()
Pandas Method
If you put the data into a pandas DataFrame, pandas will do the hard stuff for you.
import pandas as pd
coins = ['penny', 'nickle', 'dime', 'quarter']
worth = [0.01, 0.05, 0.10, 0.25]
df = pd.DataFrame(worth, columns=['1x'], index=coins)
df['2x'] = df['1x'] * 2
df['3x'] = df['1x'] * 3
df['4x'] = df['1x'] * 4
df['5x'] = df['1x'] * 5
from matplotlib import ticker
import matplotlib.pyplot as plt
df.plot(kind='bar')
plt.ylabel('Monetary Value')
plt.gca().yaxis.set_major_formatter(ticker.FormatStrFormatter('$%.2f'))
plt.gca().xaxis.set_tick_params(rotation=0)
Pandas creates a similar figure...

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