Function cv2df that accurately reads CV files into dataframe together with CV attributes.

Function works as far as I have tested.
master
Taha Ahmed 14 years ago
parent 996a79787c
commit f87e3b2a42

90
CHI.R

@ -0,0 +1,90 @@
# CHI.R
# Functions to read and manipulate data from the CHI760 potentiostat/galvanostat
# Taha Ahmed, Jan 2011
# CONTENTS
# >>>> cv2df
# >>>>
##################################################
#################### cv2df #######################
##################################################
cv2df <- function(cvfilename) {
# Function description
# CH Instruments potentiostat records all data using standard SI units,
# so all potential values are in volts, currents are in amperes,
# charges in Coulombs, time in seconds, etc.
#
cvfile <- file(cvfilename, "r")
chifile <- readLines(cvfile, n = -1) #read all lines of input file
close(cvfile)
#
rgxp.number <- "^\\-?\\d\\.\\d+,"
# regexp that matches a decimal number at the beginning of the line.
# Matches numbers with or without a negative sign (hyphen),
# followed by one digit before the decimal, a decimal point,
# and an arbitrary number of digits after the decimal point,
# immediately followed by a comma.
# Note that backslashes are escaped.
#
numrow.idx <- regexpr(rgxp.number, chifile)
# Save the match length attribute to another variable,
numrow.len <- attr(numrow.idx, "match.length")
# then scrap the attribute of the original variable.
attr(numrow.idx, "match.length") <- NULL
#
i <- seq(1, length(numrow.idx) - 1, 1)
j <- seq(2, length(numrow.idx), 1)
# Start indices of data ranges
starts <- which(numrow.idx[i] != 1 & numrow.idx[j] == 1) + 1
# End indices, except for the last
ends <- which(numrow.idx[i] == 1 & numrow.idx[j] != 1)
# Fix the last index of end indices
ends <- c(ends, length(numrow.idx))
#
ff <- data.frame(NULL)
for (s in 1:length(starts)) {
zz <- textConnection(chifile[starts[s]:ends[s]], "r")
ff <- rbind(ff,
data.frame(segment = factor(s),
matrix(scan(zz, what = numeric(), sep = ","),
ncol = 3, byrow = T)))
close(zz)
}
names(ff) <- c("segment", "potential", "current", "charge")
#
### Collect attributes of this experiment
# These attributes are specific for each kind of experiment,
# be careful when adapting to other electrochemical data
rgxp.attr <- c("^Init\\sE\\s\\(V\\)",
"^High\\sE\\s\\(V\\)",
"^Low\\sE\\s\\(V\\)",
"^Init\\sP/N",
"^Scan\\sRate\\s\\(V/s\\)",
"^Segment\\s=",
"^Sample\\sInterval\\s\\(V\\)",
"^Quiet\\sTime\\s\\(sec\\)",
"^Sensitivity\\s\\(A/V\\)")
names.attr <- c("InitE",
"HighE",
"LowE",
"InitPN",
"ScanRate",
"Segments",
"SamplingInterval",
"QuietTime",
"Sensitivity")
for (n in 1:length(rgxp.attr)) {
attrow.idx <- regexpr(rgxp.attr[n], chifile)
attrow.len <- attr(attrow.idx, "match.length")
attr(attrow.idx, "match.length") <- NULL
attr(ff, names.attr[n]) <- strsplit(chifile[which(attrow.idx == 1)],
"\\s=\\s")[[1]][2]
}
#
return(ff)
}
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