R: Methods for "[<-" - Assigning to Subsets for 'Matrix'

[<–methods {Matrix} | R Documentation

## Methods for "[<-" - Assigning to Subsets for 'Matrix'

### Description

Methods for `"[<-"`, i.e., extraction or subsetting mostly of matrices, in package Matrix.

Note: Contrary to standard `matrix` assignment in base R, in `x[..] <- val` it is typically an error (see `stop`) when the type or `class` of `val` would require the class of `x` to be changed, e.g., when `x` is logical, say `"lsparseMatrix"`, and `val` is numeric. In other cases, e.g., when `x` is a `"nsparseMatrix"` and `val` is not `TRUE` or `FALSE`, a warning is signalled, and `val` is “interpreted” as `logical`, and (logical) `NA` is interpreted as `TRUE`.

### Methods

There are many many more than these:

x = "Matrix", i = "missing", j = "missing", value= "ANY"

  is currently a simple fallback method implementation which ensures “readable” error messages.

x = "Matrix", i = "ANY", j = "ANY", value= "ANY"

  currently gives an error

x = "denseMatrix", i = "index", j = "missing", value= "numeric"

  ...

x = "denseMatrix", i = "index", j = "index", value= "numeric"

  ...

x = "denseMatrix", i = "missing", j = "index", value= "numeric"

  ...

### See Also

`[-methods` for subsetting `"Matrix"` objects; the `index` class; `Extract` about the standard subset assignment (and extraction).

### Examples

    set.seed(101)
    (a <- m <- Matrix(round(rnorm(7*4),2), nrow = 7))

    a[] <- 2.2 # <<- replaces **every** entry
    a
    ## as do these:
    a[,] <- 3 ; a[TRUE,] <- 4

    m[2, 3]  <- 3.14 # simple number
    m[3, 3:4]<- 3:4  # simple numeric of length 2

    ## sub matrix assignment:
    m[-(4:7), 3:4] <- cbind(1,2:4) #-> upper right corner of 'm'
    m[3:5, 2:3] <- 0
    m[6:7, 1:2] <- Diagonal(2)
    m

    ## rows or columns only:
    m[1,] <- 10
    m[,2] <- 1:7
    m[-(1:6), ] <- 3:0 # not the first 6 rows, i.e. only the 7th
    as(m, "sparseMatrix")

[Package Matrix version 1.1-4 Index]