plot ad hoc the sum of two columns python

Question

I have a dataframe with 2 columns namely mean and sd.

is there any way that I can plot ad hoc the summation of these two columns?

I do not want to create a third column but I want to plot the: mean + sd as one column.

In R world using ggplot you can use dplyr and do something like:

df %>% mutate(sumsd = sum+sd) %>% ggplot(.) etc without saving the data into a column.

Answer 1

The data to be plotted needs to be somewhere in memory; a dataframe column is one whay to achieve that. Assuming the following data

import numpy as np
import pandas as pd
import matplotlib.pyplot as plt

a = np.random.rand(100,20)
df = pd.DataFrame({"mean" : np.mean(a,1),
                    "std" :  np.std(a,1)})

You may now use the pandas plotting wrapper. Just add the two columns.

(df["mean"]+df["std"]).plot()

You may also sum the dataframe,

df.sum(axis=1).plot()

or if you have more columns,

df[["mean","std"]].sum(axis=1).plot()

The same can of course be done using matplotlib directly,

# case 1
plt.plot(df.index, (df["mean"]+df["std"]))
# case 2
plt.plot(df.index, df.sum(axis=1))
# case 3
plt.plot(df.index, df[["mean","std"]].sum(axis=1))