
thank you all for your help. I do know how to use which() but my problem is that I am writing a function in which this is just part of it. After seeing the (a-b)[b<a], it gives the wrong index number for which is negative and which is positive. I am not sure why that is, but the which function does give the correct index number. I guess what I want is to be able to save two vectors of index and use them to reference the raw data base for further calculation. One vector for all the negative values and one for all the positive ones. 


Edward Chen
Email: tkedch@msn.com
Cell Phone: 510-371-4717




From: wwwhsd@gmail.com
Date: Mon, 14 Sep 2009 16:35:23 -0300
Subject: Re: [R] Help with for loop
To: dwinsemius@comcast.net
CC: jorgeivanvelez@gmail.com; r-help@r-project.org; edchen51@gmail.com

Or:

(a - b)[b < a]

On Mon, Sep 14, 2009 at 4:16 PM, David Winsemius <dwinsemius@comcast.net> wrote:




On Sep 14, 2009, at 3:02 PM, Jorge Ivan Velez wrote:




Hi Edward,

Here is a suggestion:



a = c(4,5,1,7,8,12,39)

b = c(3,7,8,4,7,25,78)

d <- a-b

d[which(d>0)]

# [1] 1 3 1




#Or even:

 d <- (a-b)[which((a-b)>0)]

 d

#[1] 1 3 1






HTH,

Jorge





On Mon, Sep 14, 2009 at 2:50 PM, Edward Chen <edchen51@gmail.com> wrote:




I have a code:

*a = c(4,5,1,7,8,12,39)

b = c(3,7,8,4,7,25,78)

d =a-b

for(i in 1:length(d)){

if(d[i]>0){x = list(d[i])

print(x)}

else{y = list(d[i])

print(y)}}



the results are:



[[1]]

[1] 1



[[1]]

[1] -2



[[1]]

[1] -7



[[1]]

[1] 3



[[1]]

[1] 1



[[1]]

[1] -13



[[1]]

[1] -39





which will tell me what d is. but is it possible to output the order in

which the difference is in the vector d?

for example I would want to see x = 1,3,1 and they are from d[1], d[4],

d[5].

This is just a crude example I thought of to help me do something more

complicated.




David Winsemius, MD

Heritage Laboratories

West Hartford, CT



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