R - Changing colnames with a loop with names from another table - r

Question

I am trying to split a large dataset and
assign colnames with a loop and
save all individual data back again in a single stacked file
I am using some sample data as follows:
so firstly I split the datasets into 2 based on number of sources in the first column and read in a list using the following code:
out <- split( sample , f = sample$Source)
now I am struggling to set up a loop to change the colnames for coloumn 2 to 8
by matching the existing colnames to the following 'info' table and replacing based on source name as in the first column of the 'info' table.
the info table looks like this:
so the loop should change the colnames similar to this:
I am just wondering if anyone has done something similar could advise me?
also when I try to join them together I can only set the colnames ones using the merge function. is there any way to stack them so that I can preserve the colname for each table and looks something like this? :
my sample input files are:
> dput(sample)
structure(list(Source = structure(c(1L, 1L, 1L, 1L, 2L, 2L, 2L,
2L, 2L), .Label = c("Stack 1", "Stack 2"), class = "factor"),
year = c(2010L, 2010L, 2010L, 2010L, 2010L, 2010L, 2010L,
2010L, 2010L), day = c(1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L
), hour = c(0L, 1L, 2L, 3L, 0L, 1L, 2L, 3L, 4L), `EXIT VEL` = c(26.2,
26.2, 26.2, 26.2, 22.4, 22.4, 22.4, 22.4, 22.4), TEMP = c(341L,
341L, 341L, 341L, 328L, 328L, 328L, 328L, 328L), `STACK DIAM` = c(1.5,
1.5, 1.5, 1.5, 2.5, 2.5, 2.5, 2.5, 2.5), W = c(0L, 0L, 0L,
0L, 15L, 15L, 15L, 15L, 15L), Nox = c(39, 39, 39, 39, 33.3,
33.3, 33.3, 33.3, 33.3), Sox = c(15.5, 15.5, 15.5, 15.5,
17.9, 17.9, 17.9, 17.9, 17.9)), .Names = c("Source", "year",
"day", "hour", "EXIT VEL", "TEMP", "STACK DIAM", "W", "Nox",
"Sox"), class = "data.frame", row.names = c(NA, -9L))
> dput(stack_info)
structure(list(SNAME = structure(1:2, .Label = c("Stack 1", "Stack 2"
), class = "factor"), ISVARY = c(1L, 4L), VELVOL = c(1L, 4L),
TEMPDENS = c(0L, 2L), `DUM 1` = c(999L, 999L), `DUM 2` = c(999L,
999L), NPOL = c(2L, 2L), `EXIT VEL` = c(26.2, 22.4), TEMP = c(341L,
328L), `STACK DIAM` = c(1.5, 2.5), W = c(0L, 15L), Nox = c(39,
33.3), Sox = c(15.5, 17.9)), .Names = c("SNAME", "ISVARY",
"VELVOL", "TEMPDENS", "DUM 1", "DUM 2", "NPOL", "EXIT VEL", "TEMP",
"STACK DIAM", "W", "Nox", "Sox"), class = "data.frame", row.names = c(NA,
-2L))
thanks in advance

Answer 1

The best I ended with is this:
out <- split( sample , f = sample$Source) # your original step
stack_info[,1] <- as.character(stack_info[,1]) # To get strings column as strings and not index number later
out <- lapply( names(out), function(x) {
# Get the future names
new_cnames <- unname(unlist(stack_info[stack_info$SNAME == x,1:7]))
# replace the column names
colnames(out[[x]]) <- c("Source",new_cnames,colnames(out[[x]])[9:10] )
# Return the modified version without first column
out[[x]][,-1] })
sapply(out,write.table,append=T,file="",row.names=F,sep="|") # write (change "" to the file name you wish and sep to your desired separator and see ?write.table for more documentation)
The main idea is looping over the DF to change their colnames, I do update the list and loop again to write, you may want to append to file in the first loop.
I hope the comments are enough to get the code, tell me if it needs some details.
Output on screen (omitting warnings):
"Stack 1"|"1"|"1.1"|"0"|"999"|"999.1"|"2"|"Nox"|"Sox"
2010|1|0|26.2|341|1.5|0|39|15.5
2010|1|1|26.2|341|1.5|0|39|15.5
2010|1|2|26.2|341|1.5|0|39|15.5
2010|1|3|26.2|341|1.5|0|39|15.5
"Stack 2"|"4"|"4.1"|"2"|"999"|"999.1"|"2.1"|"Nox"|"Sox"
2010|1|0|22.4|328|2.5|15|33.3|17.9
2010|1|1|22.4|328|2.5|15|33.3|17.9
2010|1|2|22.4|328|2.5|15|33.3|17.9
2010|1|3|22.4|328|2.5|15|33.3|17.9
2010|1|4|22.4|328|2.5|15|33.3|17.9