## How to randomly select row from a dataframe for which the row skewness is larger that a given value in R

r subset dataframe by column value

r subset dataframe by list of values

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r remove rows with certain values

select rows based on column value r

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I am trying to select random rows from a data frame with 1000 lines (and six columns) where the skewness of the line is larger than a given value (say Sk > 0.3).

I've generated the following data frame

df=data.frame(replicate(6,sample(10:100,1000,rep=TRUE)))

I can get row skewness from the `fbasics`

package:

`rowSkewness(df)`

gives:

[8] -0.2243295435 0.5306809351 0.0707122386 0.0341447417 0.3339384838 -0.3910593364 -0.6443905090 [15] 0.5603809206 0.4406091534 -0.3736108832 0.0397860038 0.9970040772 -0.7702547535 0.2065830354

But now, I need to select say 10 rows of the df which have rowskewness greater than say 0.1... May with

for (a in 1:10) { sample.data[a,] = sample(x=df[wich(rowSkewness(df[sample(1:nrow(df),1)>0.1),], size = 1, replace = TRUE) }

or something like this?

Any thoughts on this will be appreciated. thanks in advance.

you can use the sample_n() function or sample_frac() - makes your version a little shorter:

library(tidyr) library(fBasics) df=data.frame(replicate(6,sample(10:100,1000,rep=TRUE))) x=df %>% dplyr::filter(rowSkewness(df)>0.1) %>% dplyr::sample_n(10)

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Got it:

x=df %>% filter(rowSkewness(df)>0.1) for (a in 1:samplesize) { sample.data[a,] = sample(x=x, size = 1, replace = TRUE) }

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Just do a subset:

res1 <- DF[fBasics::rowSkewness(DF) > .1, ] head(res1) # X1 X2 X3 X4 X5 X6 # 7 56 28 21 93 74 24 # 8 33 56 23 44 10 12 # 12 29 19 29 38 94 95 # 13 35 51 54 98 66 10 # 14 12 51 24 23 36 68 # 15 50 37 81 22 55 97

Or with `e1071::skewness`

:

res2 <- DF[apply(as.matrix(DF), 1, e1071::skewness) > .1, ] stopifnot(all.equal(res1, res2))

##### Data

set.seed(42); DF <- data.frame(replicate(6, sample(10:100, 1000, rep=TRUE)))

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##### Comments

- Thank you. What error do you get? Maybe try to load
`library(tidyverse)`

instead of`library(tidyr)`

?