🔒 axis=0 or 1? pandas

[wide cosmos]

Im getting kinda confused here.

[sturdy quiver]

@wide cosmos

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[wide cosmos]

From what ive read, axis=1 means columns, and axis=0 means rows

right

the above screenshot however shows that applying a sum function to rows returns the summation of the columns

hows that?

[echo blaze]

axis=0 means apply along axis 0, so "vertically". So it collapses each column, and returns a Series with an entry for each column.

Whereas axis=1 means apply along axis 1, so horizontally - collapsing each row into an entry, and returning a series with the same index as the dataframe.

[wide cosmos]

i mean isnt the pandas convention that axis=1 refers to columns

so instead axis=1 should refer to "applying along a column"

its not a mathematical notation

its a library convention right

[echo blaze]

Depends on what you mean. As the first index (of iloc, say) changes, you move vertically - that's what I mean by axis 0 being vertical. But df.iloc[0] is the same as df.iloc[0,:] - the first row of a dataframe.

Whereas as the second index changes, you move horizontally. So if you fix that index (while letting the first one change), you get a single column of a dataframe.

One way you could remember this is that if you do z = np.sum(arr, axis=0), that means z[i] is the sum of arr[0, i] + arr[1,i] + arr[2, i] + ... - so the zeroth axis is the one getting iterated over to do the sum.

[wide cosmos]

im still not fluent in numpy

but i may or may not have understood

i think i gotta look at numpy arrays more lol

im curious, what do you do?

[echo blaze]

numerical physics mostly, if I understand the question correctly.

[wide cosmos]

i see

so research?

[echo blaze]

sure

[wide cosmos]

interesting

well anyways

thanks mate

appreciate it

[sturdy quiver]

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