[R] For loop and using its index

[chuck.01]

Hassan, 

Others have provided you with better solutions, but I hope this allows you
to see why yours didn't work.

# first (going with your code) you needed a data.frame called "x" 
# here is an example:

x <- structure(list(x1 = c(0.0986048226696643, -0.445652024980979, 
0.0893989676314604, -3.02656448303247, -0.966125836458264,
-1.49916656636977, 
-1.43173455089552, 0.370528111260298, -1.16980816517156, -0.808744946153693
), x2 = c(-0.765406771195136, -0.37933377428095, 1.38846324586498, 
-1.70043724374807, -0.71331175577977, 1.44597103991061, 1.31674350467787, 
-0.954578441470943, -1.30637013925954, 0.551870274117374), x3 =
c(-0.122350075070145, 
1.6217818199546, -0.824570718637696, -0.0341988842898353, 1.03924814479596, 
0.898533448980663, 0.68074228601446, 0.296251937506574, -0.698501590358135, 
-0.0533564535030227)), .Names = c("x1", "x2", "x3"), row.names = c(NA, 
-10L), class = "data.frame")

# you then need an empty vector to hold the results of your for loop (called
"z" here)
# note the square brackets as opposed to your parentheses

z <- vector("list")
for (i in 1:ncol(x)) { 
z[i] = 200 - x[i] 
} 

# finally, this will reassemble the output of the for loop

z <- do.call(cbind, z)
colnames(z) <- c("z1", "z2", "z3")

# Finally, do read what the others sent you as they provide more efficient
solutions


HTH
Chuck







Hassan Eini Zinab wrote
> 
> Dear All,
> 
> I have a data set with variables x1, x2, x3, ..., x20 and I want to
> create z1, z2, z3, ..., z20 with the following formula:
> 
> 
> z1 = 200 - x1
> z2 = 200 - x2
> z3 = 200 - x3
> .
> .
> .
> z20 = 200 - x20.
> 
> 
> I tried using a for loop and its index as:
> 
> for (i in 1:20) {
> z(i) = 200 - x(i)
> }
> 
> But R gives the following error message: "Error: could not find function
> "x"".
> 
> Is there any other way for a simple coding of my 20 lines of code?
> 
> Alohas,
> Hassan Eini-Zinab
> 
> ______________________________________________
> R-help@ 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.
> 


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