Retain parts of a matrix

Hi all,

I'm working to apply a function that will generate a matrix of  
results only
when a specific criteria is met.

I want my final results to be a matrix with both the values that  
meet the
criteria (the results of the function), and those that to do in the  
same
positions in the matrix (the original numbers).

Here's a sample of what I would like to do:

t.mean.1.c <- c(-15, -20, -30, -20, -25, -35, -40, -8, 9, 10)
cdem <- c(300, 400, 700, 900, 1000, 250, 200, 300, 500, 650, 650,  
1200,
1400, 3200, 2000)
cdem.mat <- matrix(NA, 10, 15)
cdem.mat <- cdem.mat(sapply(cdem[which(cdem >= 900)], function(x)

get("t.mean.1.c") - (x * -0.0065)))

I want cdem.mat to be the same size as the the first call of it,  
with NA
values where the cdem is < 899.

I thought this would fill it in but it
seems to just over write it and I only end up with the rows where  
cdem is
greater than 900.

Thank you,

Katrina



-- 
Katrina E. Bennett
PhD Student
University of Alaska Fairbanks
International Arctic Research Center
930 Koyukuk Drive, PO Box 757340
Fairbanks, Alaska 99775-7340
907-474-1939 office
907-385-7657 cell
kebennett at alaska.edu


Personal Address:
UAF, PO Box 752525
Fairbanks, Alaska 99775-2525
bennett.katrina at gmail.com

	[[alternative HTML version deleted]]

Sorry for not being more clear.

I'll try to explain again.

I have a rather large DEM and I need to scale daily temperature  
values for 10 years.

I am using the sapply function to adjust temperatures (t.mean.1.c)  
based on lapse rates across DEM points (cdem) which meet the  
condition of elevation being greater than 300m. Below ~300m the  
lapse rate calculate changes because temperatures decrease with  
elevation. Above ~300m the lapse rates calculation must account for  
an inversion, where temperature increases with elevation.

What I would like as a result is the values of the DEM which are  
lower than 300m to retain a generic lapse rate adjustment, and the  
DEM values great than 300 to be treating using a different function.


t.mean.1.c <- c(-15, -20, -30, -20, -25, -35, -40, -8, 9, 10)
cdem <- c(300, 400, 700, 900, 1000, 250, 200, 300, 500, 650, 650,  
1200,
1400, 3200, 2000)
cdem.mat <- sapply(cdem[which(cdem >= 900)], function(x) get("t.mean. 
1.c") - (x * -0.0065)) #this just gives me a
#result of only the six values

I'm going to make this even more simple to show what I want as output.

t.mean.1.c <- c(-14, -20)
cdem <- c(300, 400, 700, 900)
cdem.mat.1 <- sapply(cdem[which(cdem >= 900)], function(x)  
get("t.mean.1.c") - (x * -0.0065))
cdem.mat.2 <- sapply(cdem[which(cdem < 900)], function(x)  
get("t.mean.1.c") + (x * -0.0065))

cdem.mat.1 #right now I get this, which is only the two temperature  
scaled to the 900 m elevation case
#       [,1]
#[1,]  -8.15
#[2,] -14.15

#What I want:

#       [,1]        [,2]   [,3]         [,4]
#[1,] -15.95  -16.6    -18.55     -8.15
#[2,] -21.95   -22.6   -24.55     -14.15

Maybe I can combine in the sapply function an if else statement? I  
haven't tested the below try.

sapply( if (cdem < 900)] function(x) get("t.mean.1.c") - (x * -0.0065)
else function(x) get("t.mean.1.c") + (x * -0.0065) )

Finally, I want to output everything into one single matrix array.

I hope that is more clear.

Thanks for your assistance.

Katrina






On Sun, Nov 27, 2011 at 7:35 PM, David Winsemius <dwinsemius at comcast.net 

wrote:

On Nov 27, 2011, at 10:15 PM, Katrina Bennett wrote:

Hi all,

I'm working to apply a function that will generate a matrix of  
results only
when a specific criteria is met.

I want my final results to be a matrix with both the values that  
meet the
criteria (the results of the function), and those that to do in the  
same
positions in the matrix (the original numbers).

Here's a sample of what I would like to do:

t.mean.1.c <- c(-15, -20, -30, -20, -25, -35, -40, -8, 9, 10)
cdem <- c(300, 400, 700, 900, 1000, 250, 200, 300, 500, 650, 650,  
1200,
1400, 3200, 2000)
cdem.mat <- matrix(NA, 10, 15)
cdem.mat <- cdem.mat(sapply(cdem[which(cdem >= 900)], function(x)
......................^
cdem.mat is not a function, cannot use "(".



get("t.mean.1.c") - (x * -0.0065)))

I want cdem.mat to be the same size as the the first call of it,  
with NA
values where the cdem is < 899.

You are only offering 10 values as replacements and an unequal  
number of condition regardless of whether you count the qualifying  
cdem conditions (6) or the total conditions(15). So you will need to  
be more clear about how you want the conditions to apply to values.  
They stepping the audience through the first few decisions and say  
where you want the values placed. Maybe you should also say whether  
you expect values to be recycled (the default with matrix assignment).

I suppose it is possible that you want the results of this:

cdem.mat[cdem>899] <-  t.mean.1.c - (cdem * -0.0065)

.... but I'm guessing not.

I thought this would fill it in but it
seems to just over write it and I only end up with the rows where  
cdem is
greater than 900.

Thank you,

Katrina



-- 
Katrina E. Bennett
PhD Student
University of Alaska Fairbanks
International Arctic Research Center
930 Koyukuk Drive, PO Box 757340
Fairbanks, Alaska 99775-7340
907-474-1939 office
907-385-7657 cell
kebennett at alaska.edu


Personal Address:
UAF, PO Box 752525
Fairbanks, Alaska 99775-2525
bennett.katrina at gmail.com

       [[alternative HTML version deleted]]

Sorry for not being more clear.

I'll try to explain again.

I have a rather large DEM and I need to scale daily temperature values for
10 years.

I am using the sapply function to adjust temperatures (t.mean.1.c) based on
lapse rates across DEM points (cdem) which meet the condition of elevation
being greater than 300m. Below ~300m the lapse rate calculate changes
because temperatures decrease with elevation. Above ~300m the lapse rates
calculation must account for an inversion, where temperature increases with
elevation.

What I would like as a result is the values of the DEM which are lower than
300m to retain a generic lapse rate adjustment, and the DEM values great
than 300 to be treating using a different function.

...