CODEWITHSUNDEEP
r
Debjyoti
Debjyoti

Reputation: 177

How to find column names based on column element in r

I have the following data frame:

1    2     3    4     5     6
P1 ca100  P4  cb100  P7   cc100
P2 ca075  P5  cb075  P8   cc075
P3 ca050  P6  cb050  P9   cc050

I want to find the names of columns which contains a particular element. For eg, if I want to find the column name containing P1, the output should be 1, the column name for any element with "ca", "cb", "cc" should be 2, 4 and 6 respectively.

Any help will be appreciated. Thanks

Upvotes: 0

Views: 504

Answers (2)

Edo
Edo

Reputation: 7818

You can wrap up str_detect from stringr in this way.

colnames_given_pattern <- function(.data, pattern){
                
  suppressWarnings(names(.data)[stringr::str_detect(.data, pattern)])
                
}
        
colnames_given_pattern(df, "P1")
#> [1] "1"
colnames_given_pattern(df, "ca")
#> [1] "2"
colnames_given_pattern(df, "ca|cb")
#> [1] "2" "4"
colnames_given_pattern(df, "ca|cb|cc")
#> [1] "2" "4" "6"

Where df is:

df <- read.table(text="
P1 ca100  P4  cb100  P7   cc100
P2 ca075  P5  cb075  P8   cc075
P3 ca050  P6  cb050  P9   cc050",header=FALSE)
names(df) <- 1:6
df
#>    1     2  3     4  5     6
#> 1 P1 ca100 P4 cb100 P7 cc100
#> 2 P2 ca075 P5 cb075 P8 cc075
#> 3 P3 ca050 P6 cb050 P9 cc050

Upvotes: 1

Julian_Hn
Julian_Hn

Reputation: 2141

We can compare each column to the element you are searching for and then return the respective colname:

df <- read.table(text="1    2     3    4     5     6
P1 ca100  P4  cb100  P7   cc100
P2 ca075  P5  cb075  P8   cc075
P3 ca050  P6  cb050  P9   cc050",header=T)


colName.of.Element <- function(df, el)
{
matched.cols <- apply(df, 2, function(col) any(col == el))
return(colnames(df[matched.cols]))
}


colName.of.Element(df,"P1")
[1] "X1"
colName.of.Element(df,"ca100")
[1] "X2"

Upvotes: 0

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