R help - Nov 2011 - 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@alaska.edu


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

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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]]
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
David Winsemius, MD
West Hartford, CT

Hi David and Jim!

Thanks very much for your help, this worked for me.

#generate two matrices that are the same size for elevation and temperature:
t.mean.1.c <- matrix(c(-15, -20, -30, -20, -25, -35, -40, -8, 9, 10),
nrow=10, ncol=15, byrow=F)
cdem <- matrix(c(300, 400, 700, 900, 1000, 250, 200, 300, 500, 650, 650,
1200, 1400, 3200, 2000),nrow=nrow(t.mean.1.c),
ncol=15, byrow=T)

#create the functions to use:
gt300 <- function(elevation,temp) return((elevation * 0.0065) + temp)
lt300 <- function(elevation,temp) return((elevation * -0.0065) + temp)

#apply the function and subset everything by the values I want to apply it
to
cdem[cdem>=300] <- gt300(cdem[cdem>=300],t.mean.1.c[cdem>=300])
cdem[cdem<300] <- lt300(cdem[cdem<300],t.mean.1.c[cdem<300])

This retains the matrix and scales everything properly.

Thanks again!

Katrina

p.s. Jim - yes, the dummy subset value I was using 900m but I switched it
in my example to my actual value (since I am going to use 300m for this
initial attempt at this). I will need to make it a lot more complicated
eventually!


On Mon, Nov 28, 2011 at 6:57 PM, Katrina Bennett
<kebennett@alaska.edu>wrote:
> Hi David and Jim!
>
> Thanks very much for your help, this worked for me.
>
> #generate two matrices that are the same size for elevation and
> temperature:
> t.mean.1.c <- matrix(c(-15, -20, -30, -20, -25, -35, -40, -8, 9, 10),
> nrow=10, ncol=15, byrow=F)
> cdem <- matrix(c(300, 400, 700, 900, 1000, 250, 200, 300, 500, 650, 650,
> 1200, 1400, 3200, 2000),nrow=nrow(t.mean.1.c),ncol=15, byrow=T)
>
> #create the functions to use:
> gt300 <- function(elevation,temp) return(temp + (elevation * 0.0065))
> lt300 <- function(elevation,temp) return(temp + (elevation * -0.0065))
>
> #apply the function and subset everything by the values I want to apply it
> to
> cdem[cdem>=300] <- gt300(cdem[cdem>=300],t.mean.1.c[cdem>=300])
> cdem[cdem<300] <- lt300(cdem[cdem<300],t.mean.1.c[cdem<300])
>
> This retains the matrix and scales everything properly.
>
> Thanks again!
>
> Katrina
>
> p.s. Jim - yes, the dummy subset value I was using 900m but I switched it
> in my example to my actual value (since I am going to use 300m for this
> initial attempt at this). I will need to make it a lot more complicated
> eventually!
>
>
>
>
> On Sun, Nov 27, 2011 at 11:41 PM, Jim Lemon <jim@bitwrit.com.au>
wrote:
>
>> On 11/28/2011 04:06 PM, Katrina Bennett wrote:
>>
>>> 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.
>>>
>>> ...
>>>
>> Hi Katrina,
>> If cdem is a matrix (and it looks like a vector in your example), you
>> could try:
>>
>> le300<-function(elevation,**temp) return(temp+elevation*0.0065)
>> gt300<-function(elevation,**temp) return(temp-elevation*0.0065)
>>
cdem[cdem<=300]<-le300(cdem[**cdem<=300],t.mean.1.c[cdem<=**300])
>>
cdem[cdem>300]<-gt300(cdem[**cdem>300],t.mean.1.c[cdem>300]**)
>>
>> where le300 is the correction for altitudes less than or equal to 300M
>> and gt300 is the one for altitudes greater than 300M. This works for me
>> with a toy function. However, I don't get the same numbers as you
and
>> wonder if your function is doing the same as the ones I use above.
Also,
>> why 300m in the text and 900m in the functions? Are we mixing up feet
and
>> meters?
>>
>> Jim
>>
>
>
>
> --
> 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@alaska.edu
>
>
> Personal Address:
> UAF, PO Box 752525
> Fairbanks, Alaska 99775-2525
> bennett.katrina@gmail.com
>
>

-- 
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@alaska.edu


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

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