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if statement problem

6 messages · Rui Barradas, Patrick Burns, reena +1 more

reena
# 
Hello,

I want to do fisher test for the rows in data file which has value less than
5 otherwise chi square test .The p values from both test should be stored in
one resulted file. but there is some problem with bold if statement. I don't
know how 
implement this line properly.


x = cbind(obs1,obs2,exp1,exp2)
a = matrix(c(0,0,0,0), ncol=2, byrow =TRUE)        #matrix with initialized
values

for (i in 1: length(x[,1]))
{
      *if((x[i,1] || x[i,2] || x[i,3] || x[i,4]) < 5)*
             {
                 a[1,1]  <- x[i,1];
                 a[1,2] <- x[i,2];
                 a[2,1] <- x[i,3];
                 a[2,2] <- x[i,4];
                 result <- fisher.test(a)
                 write.table(result[["p.value"]],file="results.txt",
sep="\n", append=TRUE, col.names=FALSE, row.names=FALSE);
               }

             else
            {
                a[1,1] <- x[i,1];
                a[1,2] <- x[i,2];
                a[2,1] <- x[i,3];
                a[2,2] <- x[i,4];
                result <- chisq.test(a)
                write.table(result[["p.value"]],file="results.txt",
sep="\n", append=TRUE, col.names=FALSE, row.names=FALSE);}
            }

Regards
R

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Rui Barradas
# 
reena wrote
Hello,
Try

*if(any(x[i,] <5))*

Merry Christmas
Rui Barradas



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Patrick Burns
# 
This is almost Circle 8.1.7 of
'The R Inferno':

http://www.burns-stat.com/pages/Tutor/R_inferno.pdf

but is making the mistake in the
other direction.
On 23/12/2011 22:40, reena wrote:

  
    

      
      
    

  


  


      

    

    

      
      

        
      

    

    

      
      

        


  

        

      Uwe Ligges
    

    

      
      #
    

  


  

      
On 24.12.2011 12:03, reena wrote:

            

      
      
      
    

        
What did not work???

Please do not misuse the R-help mailing list! Its posting guide clearly 
asks you to cite the thread and specify reproducible examples that make 
other able to help.

Best,
Uwe Ligges

            

      
      
      
    

        

      
      
    

  
  


  


      

    

    

      
      

        


  

        

      Rui Barradas
    

    

      
      #
    

  


  

      
Hello again.

I don't understand what didn't work.

First, it seems better to use 'nrow', the result is the same

 stopifnot(length(x[,1]) == nrow(x))

Then your multiple  OR condition.

#if((x[i,1] || x[i,2] || x[i,3] || x[i,4]) < 5)

x <- matrix(1:24, ncol=4)

for(i in 1:nrow(x))
	if(any(x[i,] < 5))
		cat("At least one is TRUE:", i, "\n")

for(i in 1:nrow(x))
	if((x[i,1] < 5) | (x[i,2] < 5) | (x[i,3] < 5) | (x[i,4] < 5))
		cat("The same with '|':", i, "\n")

In the second example each condition IS a condition. Unlike your original
"compound" one.
The 'Introduction to R' clearly states '|' as the union of the logical
expressions, The section is 2.4.
Also read Patrick's PDF, the parts I've read are great and very usefull.

(Thanks, Patrick, I was unaware of R inferno.pdf)

As a side note, you are duplicating the matrix 'a' assignement. Why not just
before the 'if'?
Then, you could simply test if any 'a' is less than 5.

for (i in 1: row(x))
{
           a[1,1]  <- x[i,1];
           a[1,2] <- x[i,2];
           a[2,1] <- x[i,3];
           a[2,2] <- x[i,4];
           if(any(a < 5))
             {
                    etc...
   
(Or use the compound '|' ).

Rui Barradas

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