Creating a bar plot using Seaborn - matplotlib

I am trying to plot bar chart using seaborn. Sample data:
x=[1,1000,1001]
y=[200,300,400]
cat=['first','second','third']
df = pd.DataFrame(dict(x=x, y=y,cat=cat))
When I use:
sns.factorplot("x","y", data=df,kind="bar",palette="Blues",size=6,aspect=2,legend_out=False);
The figure produced is
When I add the legend
sns.factorplot("x","y", data=df,hue="cat",kind="bar",palette="Blues",size=6,aspect=2,legend_out=False);
The resulting figure looks like this
As you can see, the bar is shifted from the value. I don't know how to get the same layout as I had in the first figure and add the legend.
I am not necessarily tied to seaborn, I like the color palette, but any other approach is fine with me. The only requirement is that the figure looks like the first one and has the legend.

It looks like this issue arises here - from the docs searborn.factorplot
hue : string, optional
Variable name in data for splitting the plot by color. In the case of ``kind=”bar”, this also influences the placement on the x axis.
So, since seaborn uses matplotlib, you can do it like this:
import matplotlib.pyplot as plt
import numpy as np
import seaborn as sns
x=[1,1000,1001]
y=[200,300,400]
sns.set_context(rc={"figure.figsize": (8, 4)})
nd = np.arange(3)
width=0.8
plt.xticks(nd+width/2., ('1','1000','1001'))
plt.xlim(-0.15,3)
fig = plt.bar(nd, y, color=sns.color_palette("Blues",3))
plt.legend(fig, ['First','Second','Third'], loc = "upper left", title = "cat")
plt.show()
Added #mwaskom's method to get the three sns colors.

Related

How to change bars' outline width in a displot?

I managed to make a displot as I intended with seaborn and the only thing I want to change is the bars' outline width. Specifically, I want to make it thinner. Here's the code and a sample of how the dataframe is composed.
import numpy as np
import pandas as pd
import matplotlib.pyplot as plt
import seaborn as sns
data_final = pd.merge(data, data_filt)
q = sns.displot(data=data_final[data_final['cond_state'] == True], y='Brand', hue='Style', multiple='stack')
plt.title('Sample of brands and their offering of ramen styles')
I'm specifying that the plot should only use rows where the cond_state is True. Here is a sample of the data_final dataframe.
Here is how the plot currently looks like.
I've tried various ways published online, but most of them use the deprecated distplot instead of displot. There also doesn't seem to be a parameter for changing the bars' outline width in the seaborn documentation for displot and FacetGrid
The documentation for the seaborn displot function doesn't have this parameter listed, but you can pass matplotlib axes arguments, such as linewidth = 0.25, to the seaborn.displot function to solve your problem.

How to plot Series with selective ticks?

I have a Series that I would like to plot as a bar chart: pd.Series([-4,2, 3,3, 4,5,9,20]).value_counts()
Since I have many bars I only want to display some (equidistant) ticks.
However, unless I actively work against it, pyplot will print the wrong labels. E.g. if I leave out set_xticklabels in the code below I get
where every element from the index is taken and just displayed with the specified distance.
This code does what I want:
import numpy as np
import pandas as pd
import matplotlib
import matplotlib.pyplot as plt
s = pd.Series([-4,2, 3,3, 4,5,9,20]).value_counts().sort_index()
mi,ma = min(s.index), max(s.index)
s = s.reindex(range(mi,ma+1,1), fill_value=0)
distance = 10
a = s.plot(kind='bar')
condition = lambda t: int(t[1].get_text()) % 10 == 0
ticks_,labels_=zip(*filter(condition, zip(a.get_xticks(), a.get_xticklabels())))
a.set_xticks(ticks_)
a.set_xticklabels(labels_)
plt.show()
But I still feel like I'm being unnecessarily clever here. Am I missing a function? Is this the best way of doing that?
Consider not using a pandas bar plot in case you intend to plot numeric values; that is because pandas bar plots are categorical in nature.
If instead using a matplotlib bar plot, which is numeric in nature, there is no need to tinker with any ticks at all.
s = pd.Series([-4,2, 3,3, 4,5,9,20]).value_counts().sort_index()
plt.bar(s.index, s)
I think you overcomplicated it. You can simply use the following. You just need to find the relationship between the ticks and the ticklabels.
a = s.plot(kind='bar')
xticks = np.arange(0, max(s)*10+1, 10)
plt.xticks(xticks + abs(mi), xticks)

How can i remove or change text from a matplotlib plot?

I have a bar plot which is being returned to me (i have access to the AxesSubplot object) which already has some labels on the bars. The issue is they are illegible and i would like to enlarge them (or clear and reset them). Take the following code for example:
import pandas as pd
import matplotlib.pyplot as plt
df = pd.DataFrame({'a':['red','green','blue'], 'b':[4,8,12]})
plot = df.plot(kind='barh')
for i in plot.patches:
plot.text(i.get_width()+.01, i.get_y()+.38, str(i.get_width()), fontsize=31)
This generates a nice bar plot with labels on the bars. But lets say i want to remove or change those labels, how can this be done?
You can access the text objects using plot.texts. In your example, you get:
>>> plot.texts
[Text(4.01,0.13,'4'), Text(8.01,1.13,'8'), Text(12.01,2.13,'12')]
You can remove them all in a loop:
for t in plot.texts:
t.set_visible(False)
Or change attributes (fontsize for example) in a similar manner:
for t in plot.texts:
# Reduce fontsize to 10:
t.set_fontsize(10)

How remove a specific legend label in the Dataframe.plot?

I am trying to plot two DataFrame together by 'bar' style and 'line' style respectively, but have trouble when showing the legend only for the bars, excluding the line.
Here are my codes:
import numpy as np
import pandas as pd
np.random.seed(5)
df = pd.DataFrame({'2012':np.random.random_sample((4,)),'2014':np.random.random_sample((4,))})
df.index = ['A','B','C','D']
sumdf = df.T.apply(np.sum,axis=1)
ax = df.T.plot.bar(stacked=True)
sumdf.plot(ax=ax)
ax.set_xlim([-0.5,1.5])
ax.set_ylim([0,3])
ax.legend(loc='upper center',ncol=3,framealpha=0,labelspacing=0,handlelength=4,borderaxespad=0)
Annoyingly got this: Figure, where the line legend is also shown in the legend box. I want to remove it rather than make it invisible.
But I do not find the way.
Thank you!
If a matplotlib.legend's label starts with an underscore, it will not be shown in the legend by default.
You can simply change
sumdf.plot(ax=ax)
to
sumdf.plot(ax=ax, label='_')

Cutting up the x-axis to produce multiple graphs with seaborn?

The following code when graphed looks really messy at the moment. The reason is I have too many values for 'fare'. 'Fare' ranges from [0-500] with most of the values within the first 100.
import pandas as pd
import numpy as np
import seaborn as sns
import matplotlib.pyplot as plt
titanic = sns.load_dataset("titanic")
y =titanic.groupby([titanic.fare//1,'sex']).survived.mean().reset_index()
sns.set(style="whitegrid")
g = sns.factorplot(x='fare', y= 'survived', col = 'sex', kind ='bar' ,data= y,
size=4, aspect =2.5 , palette="muted")
g.despine(left=True)
g.set_ylabels("Survival Probability")
g.set_xlabels('Fare')
plt.show()
I would like to try slicing up the 'fare' of the plots into subsets but would like to see all the graphs at the same time on one screen. I was wondering it this is possible without having to resort to groupby.
I will have to play around with the values of 'fare' to see what I would want each graph to represent, but for a sample let's use break up the graph into these 'fare' values.
[0-18]
[18-35]
[35-70]
[70-300]
[300-500]
So the total would be 10 graphs on one page, because of the juxtaposition with the opposite sex.
Is it possible with Seaborn? Do I need to do a lot of configuring with matplotlib? Thanks.
Actually I wrote a little blog post about this a while ago. If you are plotting histograms you can use the by keyword:
import matplotlib.pyplot as plt
import seaborn.apionly as sns
sns.set() #rescue matplotlib's styles from the early '90s
data = sns.load_dataset('titanic')
data.hist(by='class', column = 'fare')
plt.show()
Otherwise if you're just plotting value-counts, you have to roll your own grid:
def categorical_hist(self,column,by,layout=None,legend=None,**params):
from math import sqrt, ceil
if layout==None:
s = ceil(sqrt(self[column].unique().size))
layout = (s,s)
return self.groupby(by)[column]\
.value_counts()\
.sort_index()\
.unstack()\
.plot.bar(subplots=True,layout=layout,legend=None,**params)
categorical_hist(data, by='class', column='embark_town')
Edit If you want survival rate by fare range, you could do something like this
data.groupby(pd.cut(data.fare,10)).apply(lambda x.survived.sum(): x./len(x))