R help - Dec 2006 - upside down image/data

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

~~~~~~~~~~~~~~~~~~~~~~~~~~
Jennifer Barnes
PhD student - long range drought prediction
Climate Extremes
Department of Space and Climate Physics
University College London
Holmbury St Mary, Dorking
Surrey
RH5 6NT
01483 204149
07916 139187
Web: http://climate.mssl.ucl.ac.uk

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 <jmb at mssl.ucl.ac.uk>
	> Subject: [R] upside down image/data
	> To: r-help at stat.math.ethz.ch
	> Message-ID: <200612111228.kBBCSHrj013960 at msslhb.mssl.ucl.ac.uk>
	> 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

Thomas,

Thank you for this example, makes it easier to see what levelplot does - does 
this mean that EVERY time I want to plot with levelplot() I have to not only 
reverse the columns [,ncol(output.temp):1] but also have to transform the matrix
as below? I am only suprised as I don't remember having read about this in
the
R-info in ?levelplot or R-help website and it seems like a fundamental thing to 
know if using levelplot! 

Thanks,

Jenny
>
>	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 <jmb at mssl.ucl.ac.uk>
>	> Subject: [R] upside down image/data
>	> To: r-help at stat.math.ethz.ch
>	> Message-ID: <200612111228.kBBCSHrj013960 at
msslhb.mssl.ucl.ac.uk>
>	> 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
>
>
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Jennifer Barnes
PhD student - long range drought prediction
Climate Extremes
Department of Space and Climate Physics
University College London
Holmbury St Mary, Dorking
Surrey
RH5 6NT
01483 204149
07916 139187
Web: http://climate.mssl.ucl.ac.uk

Thanks Thomas,

My data arrays each contain 0.5million data points so I couldn't really 
reproduce them unfortunately. Next time I will try and offer some exapmle code 
simplified with comments in order to help you and the others on R-help 
understand my problem more easily. I appreciate your help and advise and I know 
it will be very usefull in learning about handling these huge datasets more 
accurately.

Jenny
>
>the transform that i provided orientates the data matrix so that when
plotted
with image
>or levelplot the result is isomorphic to what you see when you print the
matrix
at the r
>prompt.
>
>i don't know what your data look like---"commented, minimal,
self-contained,
reproducible
>code" would help---but you should be able to work out exactly what way
you want
your data
>to appear by playing with the example code. i would advise you to produce a 
data matrix
>the way you want to see it on the screen, just like the matrix m in the
example
code, and
>then view the output with levelplot(inverse(m)), in which case, the answer
to
your
>question is you only need to transform the data with inverse() once you get 
your data
>matrix to look the way you want at the r prompt. 
>
>
>--- Jenny Barnes <jmb at mssl.ucl.ac.uk> wrote:
>
>> Thomas,
>> 
>> Thank you for this example, makes it easier to see what levelplot does
- does
>> this mean that EVERY time I want to plot with levelplot() I have to not
only
>> reverse the columns [,ncol(output.temp):1] but also have to transform
the
matrix 
>> as below? I am only suprised as I don't remember having read about
this in
the 
>> R-info in ?levelplot or R-help website and it seems like a fundamental
thing
to 
>> know if using levelplot! 
>> 
>> Thanks,
>> 
>> Jenny
>> 
>> >
>> >	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 <jmb at mssl.ucl.ac.uk>
>> >	> Subject: [R] upside down image/data
>> >	> To: r-help at stat.math.ethz.ch
>> >	> Message-ID: <200612111228.kBBCSHrj013960 at
msslhb.mssl.ucl.ac.uk>
>> >	> 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
>> >
>> >
>> 
>> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>> Jennifer Barnes
>> PhD student - long range drought prediction
>> Climate Extremes
>> Department of Space and Climate Physics
>> University College London
>> Holmbury St Mary, Dorking
>> Surrey
>> RH5 6NT
>> 01483 204149
>> 07916 139187
>> Web: http://climate.mssl.ucl.ac.uk
>> 
>> 
>> 
>
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Jennifer Barnes
PhD student - long range drought prediction
Climate Extremes
Department of Space and Climate Physics
University College London
Holmbury St Mary, Dorking
Surrey
RH5 6NT
01483 204149
07916 139187
Web: http://climate.mssl.ucl.ac.uk