creating a new column with logical values if value in another column > 0

Question

New to R, so bear with me. I have a dataframe with values

I want to create a third column that indicates with TRUE or FALSE whether a value in column y is 0.

x y z
1 2 TRUE
0 4 TRUE
5 3 TRUE
6 0 FALSE

score 11 · Accepted Answer · answered May 07 '16 at 16:44

11

The > compares the lhs and rhs to get a logical vector. By assigning the output as a new column ('z'), we create the new column in the original dataset 'df1'.

df1$z <- df1$y > 0

answered May 07 '16 at 16:44

akrun

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It worked! I was thinking too difficult, trying stuff with the ifelse function. Thank you for the help! – Sam Nipius May 07 '16 at 16:49

score 2 · Answer 2 · answered May 07 '16 at 16:54

You can also always create one column with an "empty" value in order to avoid if-else loop.

Something like this could work as well (though the solution proposed above is of course better):

df$z <- "False"
df$z[df$y > 0] <- "True"

Quotes can be escaped if you wish a logical variable rather than a string

score 0 · Answer 3 · answered May 07 '16 at 16:59

0

An alternative solution that is faster (although this only becomes a critical issue when working with large datasets)

library(data.table)

setDT(df1)

df1[, z := y > 0]

answered May 07 '16 at 16:59

rafa.pereira

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This would work as well, data set is huge though. Thanks a lot for looking at my problem! – Sam Nipius May 07 '16 at 17:00
1

I doubt it would be noticeably faster with just one primitive computation. – Rich Scriven May 07 '16 at 17:00
I've checked here. It's a small difference indeed. Anyway, it's usually good to know alternative solutions to the same problem ;) – rafa.pereira May 07 '16 at 17:55

creating a new column with logical values if value in another column > 0

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