R help - Jan 2012 - How do I turn NA's to zeroes when a combination lacks one element?

Hi all, I am  very new to R. I am taking a course and am trying to complete
my first assignment. 
For the assignment I have to get the program to generate different color
combinations possible for a sample size of 55 with the probabilities of each
color being chosen as: .24, .24, .16, .20, .13, .14. Here is what I've come
up with... 
 
sample.size<- 55
MM.probability<- c(.24, .24, .16, .20, .13, .14)
MM.color<-
c('Bl','Br','G','O','R','Y')
mmtable<- matrix(nrow = 1000, ncol = 6)
for(i in 1:1000){
combinations<- sample(MM.color, sample.size, replace = T, prob
MM.probability)
mmtable[i,]<-table(combinations)
colnames(mmtable)<-
c("Bl","Br","G","O","R","Y")
}

I feel like it should work, but every time I run it, it usually only goes so
far (maybe to row 350, or 450, sometimes it completes with no problem)
before I start getting "NA" in every column of every row. I also get
this
error message "Error in mmtable[i, ] <- table(combinations) :  number of
items to replace is not a multiple of replacement length"
Someone suggested that it is because the program is coming upon a
combination that is missing one of the colors, so I'd have to instruct it to
put a zero in place of the missing color so the simulation can continue,
which completely makes sense. But I've been trying and can't figure out
how
to do it. I tried "mmtable[is.na(mmtable)]<-0", but then I just get
zeroes
everywhere instead of NA's, and "mmtable[na.omit(mmtable)]" gives
me the
same as no instruction at all. Do you know what the right notation would be?
I also need to use the script to determine the probability of getting the
combination with proportions: .182, .164, .309, .145, .091, .1090. I've also
tried a few things for this and am coming up with nothing. Sorry if this is
a really simple question, I am sure most of you could do this in your sleep,
but it's all very new to me. Thanks in advance. 

-C

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On 29-01-2012, at 18:18, C_Crown wrote:
> Hi all, I am  very new to R. I am taking a course and am trying to complete
> my first assignment. 
> For the assignment I have to get the program to generate different color
> combinations possible for a sample size of 55 with the probabilities of
each
> color being chosen as: .24, .24, .16, .20, .13, .14. Here is what I've
come
> up with... 
> 
> sample.size<- 55
> MM.probability<- c(.24, .24, .16, .20, .13, .14)
> MM.color<-
c('Bl','Br','G','O','R','Y')
> mmtable<- matrix(nrow = 1000, ncol = 6)
> for(i in 1:1000){
> combinations<- sample(MM.color, sample.size, replace = T, prob >
MM.probability)
> mmtable[i,]<-table(combinations)
> colnames(mmtable)<-
c("Bl","Br","G","O","R","Y")
> }
> 
> I feel like it should work, but every time I run it, it usually only goes
so
> far (maybe to row 350, or 450, sometimes it completes with no problem)
> before I start getting "NA" in every column of every row. I also
get this
> error message "Error in mmtable[i, ] <- table(combinations) : 
number of
> items to replace is not a multiple of replacement length"
> Someone suggested that it is because the program is coming upon a
> combination that is missing one of the colors, so I'd have to instruct
it to
> put a zero in place of the missing color so the simulation can continue,
> which completely makes sense. But I've been trying and can't figure
out how
> to do it.
This is homework. "Someone's"  guess as to what is causing the
problem is correct.
However:

Create mmtable as a matrix with all 0's and give the columns the names of
colors.
Like this

mmtable  <- matrix(0, nrow = 1000, ncol = 6, dimnames=list(c(),MM.color))

Then in the loop replace the lines 

mmtable[i,]<-table(combinations)
colnames(mmtable)<-
c("Bl","Br","G","O","R","Y")

with

    z <- table(combinations)
    mmtable[i,names(z)] <- z

The second line stores the entries in z in the columns with the same column name
and leaves the others alone.

Since you initialized mmtable with 0's you won't need to replace
NA's with 0.

Berend

?ifelse

Type that in and you'll be in good shape.

On 1/29/12, C_Crown <ccrown at life.bio.sunysb.edu>
wrote:
> Hi all, I am  very new to R. I am taking a course and am trying to complete
> my first assignment.
> For the assignment I have to get the program to generate different color
> combinations possible for a sample size of 55 with the probabilities of
each
> color being chosen as: .24, .24, .16, .20, .13, .14. Here is what I've
come
> up with...
>
> sample.size<- 55
> MM.probability<- c(.24, .24, .16, .20, .13, .14)
> MM.color<-
c('Bl','Br','G','O','R','Y')
> mmtable<- matrix(nrow = 1000, ncol = 6)
> for(i in 1:1000){
> combinations<- sample(MM.color, sample.size, replace = T, prob >
MM.probability)
> mmtable[i,]<-table(combinations)
> colnames(mmtable)<-
c("Bl","Br","G","O","R","Y")
> }
>
> I feel like it should work, but every time I run it, it usually only goes
so
> far (maybe to row 350, or 450, sometimes it completes with no problem)
> before I start getting "NA" in every column of every row. I also
get this
> error message "Error in mmtable[i, ] <- table(combinations) : 
number of
> items to replace is not a multiple of replacement length"
> Someone suggested that it is because the program is coming upon a
> combination that is missing one of the colors, so I'd have to instruct
it to
> put a zero in place of the missing color so the simulation can continue,
> which completely makes sense. But I've been trying and can't figure
out how
> to do it. I tried "mmtable[is.na(mmtable)]<-0", but then I
just get zeroes
> everywhere instead of NA's, and "mmtable[na.omit(mmtable)]"
gives me the
> same as no instruction at all. Do you know what the right notation would
be?
> I also need to use the script to determine the probability of getting the
> combination with proportions: .182, .164, .309, .145, .091, .1090. I've
also
> tried a few things for this and am coming up with nothing. Sorry if this is
> a really simple question, I am sure most of you could do this in your
sleep,
> but it's all very new to me. Thanks in advance.
>
> -C
>
> --
> View this message in context:
>
http://r.789695.n4.nabble.com/How-do-I-turn-NA-s-to-zeroes-when-a-combination-lacks-one-element-tp4338725p4338725.html
> Sent from the R help mailing list archive at Nabble.com.
>
> ______________________________________________
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> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>
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