Hi,
I have some very large (~1.1 GB) output files from a groundwater model called
STOMP that I want to read as efficiently as possible. For each variable there
are over 1 million values to read. Variables are not organized in columns;
instead they are written out in sections in the file, like this:
X-Direction Node Positions, m
5.931450000E+05 5.931550000E+05 5.931650000E+05 5.931750000E+05
5.932450000E+05 5.932550000E+05 5.932650000E+05 5.932750000E+05
. . .
5.946950000E+05 5.947050000E+05 5.947150000E+05 5.947250000E+05
5.947950000E+05 5.948050000E+05 5.948150000E+05 5.948250000E+05
Y-Direction Node Positions, m
1.148050000E+05 1.148050000E+05 1.148050000E+05 1.148050000E+05
1.148050000E+05 1.148050000E+05 1.148050000E+05 1.148050000E+05
. . .
1.171950000E+05 1.171950000E+05 1.171950000E+05 1.171950000E+05
1.171950000E+05 1.171950000E+05 1.171950000E+05 1.171950000E+05
Z-Direction Node Positions, m
9.550000000E+01 9.550000000E+01 9.550000000E+01 9.550000000E+01
9.550000000E+01 9.550000000E+01 9.550000000E+01 9.550000000E+01
. . .
I want to read and use only a subset of the variables. I wrote the function
below to find the line where each target variable begins and then scan the
values, but it still seems rather slow, perhaps because I am opening and
closing the file for each variable. Can anyone suggest a faster way?
# Reads original STOMP plot file (plot.*) directly. Should be useful when the
plot files are
# very large with lots of variables, and you just want to retrieve a few of
them.
# Arguments: 1) plot filename, 2) number of nodes,
# 3) character vector of names of target variables you want to return.
# Returns a list with the selected plot output.
READ.PLOT.OUTPUT6 <- function(plt.file, num.nodes, var.names) {
lines <- readLines(plt.file)
num.vars <- length(var.names)
tmp <- list()
for(i in 1:num.vars) {
ind <- grep(var.names[i], lines, fixed=T, useBytes=T)
if(length(ind) != 1) stop("Not one line in the plot file with matching
variable name.\n")
tmp[[i]] <- scan(plt.file, skip=ind, nmax=num.nodes, quiet=T)
}
return(tmp)
} # end READ.PLOT.OUTPUT6()
Regards,
Scott Waichler
Pacific Northwest National Laboratory
Richland, WA, USA
scott.waich...@pnnl.gov
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