R help - Feb 2010 - Help with assigning values to a row or column

Hello,

I am attempting to write a function that assigns a value to a row or column
within the matrix that it runs on. I am, however, having trouble accessing
the row or column within this dynamic variable. I have looked through the
archives (nothing there) and read the rules for posting to this list. Please
help me out!

Here is a sample of the problem:


testMatrix = matrix(data=2, nrow=10, ncol=10)

testFunction = function (input)
{
    inputName <<- deparse(substitute(input))

    assign(inputName[1,], 4, envir = .GlobalEnv)
}

#this will give you the error
testFunction(testMatrix)


When I try to access "inputName[1,]" instead of "inputName,"
it fails. Does
anyone know how to do this?

Thanks in advance!!


Best Regards,

Dave Deriso
Undergraduate Researcher
UCSD Psychiatry

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Hello,

With a little broader searching, I did find a solution by Fernando Saldanha
(http://tolstoy.newcastle.edu.au/R/help/05/04/3559.html):

eval(parse(text = paste('testMatrix', '[1,] <- 4', sep =
'')))

Thanks anyway!!

Best,

Dave



On Mon, Feb 8, 2010 at 12:19 AM, Dave Deriso <dderiso@ucsd.edu> wrote:
> Hello,
>
> I am attempting to write a function that assigns a value to a row or column
> within the matrix that it runs on. I am, however, having trouble accessing
> the row or column within this dynamic variable. I have looked through the
> archives (nothing there) and read the rules for posting to this list.
Please
> help me out!
>
> Here is a sample of the problem:
>
>
> testMatrix = matrix(data=2, nrow=10, ncol=10)
>
> testFunction = function (input)
> {
>     inputName <<- deparse(substitute(input))
>
>     assign(inputName[1,], 4, envir = .GlobalEnv)
> }
>
> #this will give you the error
> testFunction(testMatrix)
>
>
> When I try to access "inputName[1,]" instead of
"inputName," it fails.
> Does anyone know how to do this?
>
> Thanks in advance!!
>
>
> Best Regards,
>
> Dave Deriso
> Undergraduate Researcher
> UCSD Psychiatry
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