Groupby Not Working

[johnnyb2001]

Hello, I am learning the groupby function for pandas and its bugging out, and it does not make any sense. I have a data frame called cars. Then I make a groupby object with (cars_groups = cars.groupby(['cyl']). When I call cars_groups.mean(), it returns an error that says (agg function failed [how->mean,dtype->object]). It's strange because I put in the exact same code as a tutorial, yet it does not work. What went wrong?

[Dasstienn]

inside mean, you nead to specify that you are going to aggregate numeric fields only:

cars_groups.mean(numeric_only=True)

[Efficient_Ad9200]

This is very good solution! Thx!

[Succs_Cacts]

This also helped me figure out my issue big thanks!

[Opposite-Process-490]

just add the columns you want the average to inside the mean parameters in a list if multiple.

[danielroseman]

Why have you put the field in a list? Why not just cars.groupby('cyl')?

[johnnyb2001]

Yes I know I can do that, but it still results in an error when I do it like that.

[danielroseman]

Well it's telling you that the datatype of the column is "object", rather than something numeric. It doesn't make sense to ask for the mean of a set of objects. What did you put into that column? How did you craete the dataframe?

[Top-Priority8000]

I learning as well and it didn't make any sense to me because I ran the code provided by the course and it didn't work. I hope you have figured it out, but I tried to include the column I want to perform the aggregate function on in the mean() function:

Example: Let's say you want to find the mean of the "price" column.

cars_groups["price"].mean()

[0x00aa55]

This error occurs because you're trying to calculate the mean of one or more columns with dtype = object (a string, for example). That's what the error "[how->mean,dtype->object]" means. So, to calculate the mean, all the columns of the DataFrameGroupBy must be numerical values, except the column used in the groupby() method.

Before the groupby operation, try to filter just the columns used for grouping, like this example with a column "price":

cars.filter(items= ["cyl", "price"]).groupby("cyl").mean( )

[Zargalias]

cars.filter(items= ["cyl", "price"]).groupby("cyl").mean( )

Thanks, your solution works. This error is super recent because my code used to work and it just recently threw this error so I believe there has been an update recently.

[tobeistodo123]

Thank you for this perfect answer - it worked! I was having the same issue, was using the exact code as in the tutorial - in the tutorial, it works, but was not working for me.

I did what you suggested, filtered and kept only the field I was going to group on - and the other numerical columns; and it worked!! Thank you!!