Average of multiple rows based on column condition in Python

Question

How do I get the average from multiple rows where column stage = 2.

At the moment I am using

average = df.loc[df.Stage == 2,'Vout'].mean()

However, this returns an average based off the entire column.

I want to have multiple average values based off certain rows, as there is multiple blocks of data.

Sample Data

Any help would be great! Thanks.

You want the mean of rows 5, 7 & 8 (1054, 1031, 1031) separate from the mean of rows 12, 14 & 15 (2, 1046, 1040)? — Paul
– Paul, Commented Dec 6, 2021 at 13:31
Yes @Paul, as there will be multiple blocks of data just like these. — fudgey
– fudgey, Commented Dec 6, 2021 at 13:41
You will need to assign a specific value to these blocks. so you can group by them, I believe @jezrael did it in his answer. — Paul
– Paul, Commented Dec 6, 2021 at 13:47

jezrael · Accepted Answer · 2021-12-06 13:45:13Z

1

If possible distinguish group by missing values use:

df['g'] = df['Stage'].isna().cumsum()

average = df.loc[df.Stage == 2].groupby('g')['Vout'].mean()

answered Dec 6, 2021 at 13:45

jezrael

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1 Comment

Using this I get ``` cannot convert g ```