CODEWITHSUNDEEP
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user2795569
user2795569

Reputation: 343

Apply function to remove columns R

I have a large data frame. I need to go through and test the first row of values and remove the columns if the value in the first row isn't below a certain threshold.

red <- c(1,2,3)
blue <- c(4, 5, 4)
colors <- data.frame(red, blue)
colors <- t(colors)
colors
     [,1] [,2] [,3]
red     1    2    3
blue    4    5    4

How would I, for example, keep only columns that have a red value below 2.5?

Thanks so much! Im still pretty new to this!

Upvotes: 0

Views: 158

Answers (2)

Jilber Urbina
Jilber Urbina

Reputation: 61214

Try this

> colors[,colors[1, ]<2.5 ]
     [,1] [,2]
red     1    2
blue    4    5

Upvotes: 2

Paul Hiemstra
Paul Hiemstra

Reputation: 60984

You could do something like:

> colors[,colors['red',] < 2.5]
     [,1] [,2]
red     1    2
blue    4    5

Where you don't use an apply function, but vectorization in stead. The expression colors['red',] < 2.5 leads to an logical vector (TRUE, FALSE) with TRUE where the expression is valid, and FALSE where it is not. You can use this logical vector to index colors, where using colors[, logical_vector] ensures you use the logical vector to index columns.

Upvotes: 2

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