Using pandas to create rate of change in a variable-CodePudding

I have a pandas dataset that looks at the number of n cases of an instance over time.

I have sorted the dataset in ascending order from the first recorded date and have created a new column called 'change'.

I am unsure however how to take the data from column n and map it onto the 'change' column such that each cell in the 'change' column represents the difference from the previous day.

For example, if on day 334 there were n = 14000 and on day 335 there were n = 14500 cases, in that corresponding 'change' cell I would want it to say '500'.

I have been trying things out for the past couple of hours but to no avail so have come here for some help.

I know this is wordier than I would like, but if you need any clarification let me know.

CodePudding user response：

import pandas as pd

df = pd.DataFrame({
        'date': [1,2,3,4,5,6,7,8,9,10], 
        'cases': [100, 120, 129, 231, 243, 212, 375, 412, 440, 1]
    })

df['change'] = df.cases.diff()

OUTPUT

   date  cases  change
0     1    100     NaN
1     2    120    20.0
2     3    129     9.0
3     4    231   102.0
4     5    243    12.0
5     6    212   -31.0
6     7    375   163.0
7     8    412    37.0
8     9    440    28.0
9    10      1  -439.0