R multiple regular expressions, dataframe column names - r

Question

I have a dataframe data with a lot of columns in the form of
...v1...min ...v1...max ...v2...min ...v2...max
1 a a a a
2 b b b b
3 c c c c
where in place ... there could be any expression.
I would like to create a function createData that takes three arguments:
X: a dataframe,
cols: a vector containing first part of the column, so i.e. c("v1", "v2")
fun: a vector containing second part of the column, so i.e. c("min"), or c("max", "min")
and returns filtered dataframe, so - for example:
createData(X, c("v1"), None) would return this kind of dataframe:
...v1...min ...v1...max
1 a a
2 b b
3 c c
while createData(X, c("v1", "v2"), c("min")) would give me
...v1...min ...v2...min
1 a a
2 b b
3 c c
At this point I decided I need to use i.e. select(contains()) from dplyr package.
createData <- function(data, fun, cols)
{
X %>% select(contains())
return(X)
}
What I struggle with is:
how to filter columns that consist two (or maybe more?) strings, i.e. both var1 and min? I tried going with data[grepl(".*(v1*min|min*v1).*", colnames(data), ignore.case=TRUE)] but it doesn't seem to work and also my expressions aren't fixed - they depend on the vector I pass,
how to filter multiple columns with different names, i.e. c("v1", "v2"), passed in a vector? and how to combine it with the first question?
I don't really need to stick with dplyr package, it was just for the sake of the example. Thanks!
EDIT:
An reproducible example:
data = data.frame(AXv1c2min = c(1,2,3),
subv1trwmax = c(4,5,6),
ss25v2xxmin = c(7,8,9),
cwfv2urttmmax = c(10,11,12))

Answer 1

If you pass a vector to contains, it will function like an OR tag, while multiple select statements will have additive effects. So for your esample data:
We can filter for (v1 OR v2) AND min like this:
library(tidyverse)
data %>%
select(contains(c('v1','v2'))) %>%
select(contains('min'))
AXv1c2min ss25v2xxmin
1 1 7
2 2 8
3 3 9
So as a function where either argument is optional:
createData <- function(data, fun=NULL, cols=NULL) {
if (!is.null(fun)) data <- select(data, contains(fun))
if (!is.null(cols)) data <- select(data, contains(cols))
return(data)
}
A series of examples:
createData(data, cols=c('v1', 'v2'), fun='min')
AXv1c2min ss25v2xxmin
1 1 7
2 2 8
3 3 9
createData(data, cols=c('v1'))
AXv1c2min subv1trwmax
1 1 4
2 2 5
3 3 6
createData(data, fun=c('min'))
AXv1c2min ss25v2xxmin
1 1 7
2 2 8
3 3 9
createData(data, cols=c('v1'), fun=c('min', 'max'))
AXv1c2min subv1trwmax
1 1 4
2 2 5
3 3 6
createData(data, cols=c('v1'), fun=c('max'))
subv1trwmax
1 4
2 5
3 6