在R中使用grepl计算要匹配的模式字符串的数量

Question

I've written a script related to data analysis and I'm trying to make it as flexible as possible so that it will be useful to multiple teams that store/use their data in different ways. I'm also trying to make it as simple to use as possible because I know people using it won't be as adept at R as I am. I have a couple of user-defined variables that must be changed before use:

headers = "B|M1|M2|M3"
keepscore = 3

I use this information to remove columns of unnecessary data by finding the strings in "headers" and keeping only those columns:

x = x[ ,grepl(headers, names(x))]

"M1", "M2", and "M3" are columns that contain data to keep for analysis, but the number of these columns is variable dependent on the team. "keepscore" is the number of those columns. Rather than having to have the user enter "keepscore" = 3, what I want to do is have the script extrapolate how many search strings there are in headers. The number of strings is 4, so keepscore should be 4 - 1 = 3. So, is there a way to count the number of search strings in "headers"?

Answer 1

Are you looking for this :

length(unlist(strsplit(headers,'|',fixed=TRUE)))-1

## [1] 3