CODEWITHSUNDEEP
rmatrix
Abaddon666
Abaddon666

Reputation: 1623

R Matrix: Set Single Value of name referenced matrix

I have matrices stored in variables i create out if strings through assign( name, matrix(...) ) Now i want to set a single value of this matrix providing its name, the row and col and the new value. I would have imagined it like this:

get(name, envir = my.env)[x,y] <- value

or

assign(paste(name,"[",x,",",y,"]"),value, envir = my.env)

But both options do not work. Is there any nice way to adress this one particular field of the matrix? My current workaround is to first save the matrix to a variable, set its value and set the matrix back to its original variable. It seems to me it is copying the matrix here as it leads to memory problems (the matrix is very big). I obviusoly would prefer other solutions

Upvotes: 0

Views: 151

Answers (2)

cogitovita
cogitovita

Reputation: 1735

Try eval:

my.env <- new.env()
name = 'd'
x = y = 1
assign(name, matrix(1:4, 2), envir=my.env)
eval(parse(text=paste(name, '[', x, ',', y, '] = ', value)), envir=my.env)
my.env[[name]]
#      [,1] [,2]
# [1,]    0    3
# [2,]    2    4

Upvotes: 0

Roland
Roland

Reputation: 132736

Usually I would use a list, but you can work with an environment in pretty much the same way:

my.env <- new.env()
myname <- "mymat"
assign(myname, matrix(1:16, 4), envir = my.env)
my.env[[myname]][1, 1] <- 42
my.env[[myname]]
#     [,1] [,2] [,3] [,4]
#[1,]   42    5    9   13
#[2,]    2    6   10   14
#[3,]    3    7   11   15
#[4,]    4    8   12   16

Upvotes: 2

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