How to find total amount of columns with a specific word in a dataframe

so I am trying to find the number of samples that are labelled with the phrase 'PaperB' in a very larger data frame in R, I have used the following:

df[grep("PaperB", names(df))]

but this has given me all the columns labelled with Tissue B and their values, rather than the total amount of PaperB samples, how could i change this to just get the total amount?

thanks for any help

CodePudding user response：

strong textIf I understood you correctly: Here is dplyr solution using the iris dataset: Here we count the columns that contain the string "Sepal" in their name with length() function:

library(dplyr)
iris %>% 
  select(contains("Sepal")) %>% 
  length()

[1] 2

BASE R For you code we would do:

length(iris[grep("Sepal", names(iris))])

CodePudding user response：

As the data frame is large I would avoid pulling its data and deal only with metadata. You were very close:

cn <- colnames(iris) 
gr <- grep("PaperB", cn)
length(gr)

Or in a pipeline:

cn <- colnames(iris) 
grep("PaperB", cn) |>
  length()