accessing the rows in vaex dataframe.

[RAJAT8878]

In pandas, we have a facility for accessing the rows from loc or iloc method. Is there any way by which we can access the specific rows for vaex dataframe.

[maartenbreddels]

Vaex has no index (yet), so by default all access is row based.
This should work.

import vaex
df = vaex.example()
df['x'].values[0]

Note that if x is virtual column, every time you access .values it will have to be computed (thus slow). So you may want to assign it to a local variable. If x is too large, you may want to get a chunk:

import vaex
df = vaex.example()
chunk = df['x'][:10000].values
chunk[0]

What is the reason to access an individual value, may I ask?

[RAJAT8878]

Hi @maartenbreddels It's not about accessing an individual value or not any columns value. Let's suppose i wanted to filter by index where index is in timestamp format. since loc and iloc is very common for selecting the subset of data based on the condition.

[maartenbreddels]

Could you be more specific on what you want, like give a pandas example? Thanks!

[JovanVeljanoski]

Will close this as stale - please reopen if needed. Thanks!

[calebjacksonhoward]

How might I do this sort of selective modification of a vaex dataframe?

import pandas as pd
import numpy as np

id      = [2, 3, 7, 9, 10, 11]
truth   = [False, False, False, False, False, False]
df      = pd.DataFrame({'id': id, 'truth': truth})

filter      = [3, 10]
selection   = [i in filter for i in id]

df.loc[selection, 'truth'] = True

print(df)

[vijaybabupalli]

In pandas, we have a facility for accessing the rows from loc or iloc method. Is there any way by which we can access the specific rows for vaex dataframe.

[FrancescoSaverioZuppichini]

any update?

[NickCrews]

FYI the issue is closed, so maintainers aren't going to look at it. Open a new issue if you need it, and please be specific with what you need. The solution that was posted works great for accessing specific rows and columns.

@calebjacksonhoward, for selective modifcation, you need to use where(): https://vaex.io/docs/api.html#vaex.expression.Expression.where

[chaoshunihao]

import vaex
df=vaex.example()
df[1:5]