cbind<- {str2str}

Add Columns to Data Objects

Description

`cbind<-` adds columns to data objects as a side effect. The purpose of the function is to replace the need to use dat2 <- cbind(dat1, add1); dat3 <- cbind(dat2, add2); dat4 <- cbind(dat3, add3), etc. For data.frames, it functions similarly to `[<-.data.frame`, but allows you to specify the location of the columns similar to append (vs. c) and overwrite columns with the same colnames. For matrices, it offers more novel functionality since `[<-.matrix` does not exist.

Usage

cbind(data, after = ncol(data), col.nm = NULL, overwrite = TRUE) <- value

Arguments

data

data.frame or matrix of data.

after

either an integer vector with length 1 or a character vector of length 1 specifying where to add value. If an integer vector, it is the position of a column. If a character vector it is the column with that name. Similar to append, use 0L if you want the added columns to be first.

col.nm

character vector of length equal to NCOL(value) that specifies the colnames of value once added to data as columns. This is an optional argument that defaults to NULL where the pre-existing colnames of value are used.

overwrite

logical vector of length 1 specifying whether columns from value or col.nm should overwrite columns in data with the same colnames. Note, if overwrite = FALSE, repeat colnames are possible similar to cbind.

value

data.frame, matrix, or atomic vector to be added as columns to data. If a data.frame or matrix, it must have the same nrow as data. If an atomic vector, it must have length equal to nrow of data. Note, if it is an atomic vector and col.nm is NULL, then the name of the added column will be "value".

Details

Some traditional R folks may find this function uncomfortable. R is famous for limiting side effects, except for a few notable exceptions (e.g., `[<-` and `names<-`). Part of the reason is that side effects can be computationally inefficient in R. The entire object often has to be re-constructed and re-saved to memory. For example, a more computationally efficient alternative to cbind(dat) <- add1; cbind(dat) <- add2; cbind(dat) <- add3 is dat1 <- do.call(what = cbind, args = list(dat, add1, add2, add3)). However, `cbind<-` was not created for R programming use when computational efficiency is valued; it is created for R interactive use when user convenience is valued.

Similar to `cbind`, `cbind<-` works with both data.frames and matrices. This is because `cbind` is a generic function with a default method that works with matrices and a data.frame method that works with data.frames. Similar to `cbind`, if colnames of value are not given and col.nm is left NULL, then the colnames of the return object are automatically created and can be dissatisfying.

Value

Like other similar functions (e.g., `names<-` and `[<-`), `cbind<-` does not appear to have a return object. However, it technically does as a side effect. The argument data will have been changed such that value has been added as columns. If a traditional return object is desired, and no side effects, then it can be called like a traditional function: dat2 <- 'cbind<-'(dat1, value = add1).

Examples

attitude2 <- attitude
cbind(attitude2) <- rowMeans(attitude2) # defaults to colnames = "value"
attitude2["value"] <- NULL
cbind(attitude2, col.nm = "mean") <- rowMeans(attitude2) # colnames specified by `col.nm`
attitude2["mean"] <- NULL
cbind(attitude2, after = "privileges", col.nm = c("mean","sum")) <-
   cbind(rowMeans(attitude2), rowSums(attitude2)) # `value` can be a matrix
attitude2[c("mean","sum")] <- NULL
attitude2 <- `cbind<-`(data = attitude2, value = rowMeans(attitude2)) # traditional call
attitude2["value"] <- NULL
cbind(attitude2, after = "privileges", col.nm = "mean") <-
   rowMeans(attitude2) # `data` can be a matrix
cbind(attitude2) <- data.frame("mean" = rep.int(x = "mean", times = 30L)) # overwrite = TRUE
cbind(attitude2, overwrite = FALSE) <-
   data.frame("mean" = rep.int(x = "mean", times = 30L)) # overwrite = FALSE
cbind(attitude2) <- data.frame("mean" = rep.int(x = "MEAN", times = 30L),
   "sum" = rep.int(x = "SUM", times = 30L)) # will overwrite only the first "mean" column
   # then will append the remaining columns