I have a certain feature in my data which looks like this:

I'm trying to introduce cumulative sum this column in the DataFrame as following (the feature is int64 type):

df['Cumulative'] = df['feature'].cumsum()

But for unknown reason I have a drop in this function which is weird since the min number in the original column is 0:

Can someone explain why this happens and how can I fix that.Because I just want to sum the feature as it appears.

Thank you in advance.

CodePudding user response：

Like in the comments suggested, sorting first and after that build the cumulative sum. Did you try it like this:

df = df.sort_values(by='Date') #where "Date" is the column name of the values on the x-axis
df['cumulative'] = df['feature'].cumsum()