rm(list=ls(all=TRUE))
graphics.off()
# make a test matrix:
nr<- 3
nc<- 4
# the data:
( m<- matrix((1:(nr*nc)), nr, nc) )
[,1] [,2] [,3] [,4]
[1,] 1 4 7 10
[2,] 2 5 8 11
[3,] 3 6 9 12
# the way that levelplot (and image) displays the data:
t(m)[dim(t(m))[1]:1, ]
[,1] [,2] [,3]
[1,] 10 11 12
[2,] 7 8 9
[3,] 4 5 6
[4,] 1 2 3
# undo what levelplot does by performing the inverse transformation
inverse<- function(x) t(x[dim(x)[1]:1, ])
windows(); levelplot(m, main="levelplot(m)")
windows(); levelplot(inverse(m), main="levelplot(inverse(m))")
> Message: 7
> Date: Mon, 11 Dec 2006 12:28:17 +0000 (GMT)
> From: Jenny Barnes <[EMAIL PROTECTED]>
> Subject: [R] upside down image/data
> To: [email protected]
> Message-ID: <[EMAIL PROTECTED]>
> Content-Type: TEXT/plain; charset=us-ascii
>
> Dear R-community,
>
> I am looking for some simple advice - I have a matrix (therefore 2
dimensional)
> of global temperature.
>
> Having read R-help I think that when I ask R to image() or
levelplot() my matrix
> will it actually appear upside down - I think I therefore need to use
the line:
> > levelplot(temperature.matrix[,ncol(output.temp):1], ........)
> to get it looking like it was on the globe due to the matrix rows
increasing in
> number down the matrix in its dimensions on longitude and latitude
but the
> y-axis coordinates increase up the axis.
>
> Can anyone simply tell me whether this is correct as I find it very
hard to know
> which way up my data should be and I cannot tell which is correct
simply by
> looking at it!
>
> Many thanks for your time in reading this problem,
>
> Jenny Barnes
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