You cannot select more than 25 topics Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.

147 lines
5.9 KiB
R

source("/home/taha/chepec/chetex/common/R/common.R")
##################################################
################### mps2df #######################
##################################################
mps2df <- function(datafilename, wearea = 1) {
## Description:
## Reads time vs current data (from CHI 760 potentiostat)
## and returns a dataframe with the data and
## the data attributes (experimental conditions).
## Usage:
## mps2df(datafilename, wearea)
## Arguments:
## datafilename: text string with full path to experimental file
## wearea: working electrode area in square centimeters (optional)
## Value:
## Dataframe with the following columns (and no extra attributes):
## $ sampleid : chr
## $ time : num
## $ current : num
## $ currentdensity : num
## $ timediff : num
## $ dIdt : num
## $ didt : num
## $ charge : num
## $ chargedensity : num
## $ PotentialSteps : num
## $ TimeSteps : num
## $ Cycle : num
## $ SampleInterval : num
## $ QuietTime : num
## $ Sensitivity : num
## Note:
## The CH Instruments 760 potentiostat records all data
## using standard SI units, therefore this function
## assumes all potential values to be in volts,
## currents to be in amperes, charges in Coulombs,
## time in seconds, and so on.
#
datafile <- file(datafilename, "r")
chifile <- readLines(datafile, n = -1) #read all lines of input file
close(datafile)
#
sampleid <- ProvideSampleId(datafilename)
#
rgxp.number <- "^\\-?\\d+\\.\\d+[e,]"
# 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 either the letter 'e' or a comma.
# Note that backslashes are escaped due to the way R handles strings.
#
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(stringsAsFactors = FALSE,
sampleid, matrix(scan(zz, what = numeric(), sep = ","),
ncol = 2, byrow = T)))
close(zz)
}
names(ff) <- c("sampleid", "time", "current")
# Calculate current density
currentdensity <- ff$current / wearea
ff <- cbind(ff, currentdensity = currentdensity)
# Calculate time diff and current diff
timediff <- c(ff$time[1], diff(ff$time))
currentdiff <- c(ff$current[1], diff(ff$current))
currentdensitydiff <- c(ff$currentdensity[1], diff(ff$currentdensity))
# Calculate differential of current and current density
dIdt <- currentdiff / timediff
didt <- currentdensitydiff / timediff
# Calculate charge and charge density
charge <- cumsum(ff$current)
chargedensity <- cumsum(ff$currentdensity)
# Update ff dataframe
ff <- cbind(ff,
timediff = timediff,
dIdt = dIdt,
didt = didt,
charge = charge,
chargedensity = chargedensity)
#
### Collect attributes of this experiment
# Potential steps
PotentialSteps <- ""
positions.PotentialSteps <- regexpr("^E\\d+\\s\\(V\\)", chifile)
PotentialSteps <- paste("\\num{", strsplit(chifile[which(positions.PotentialSteps == 1)],
"\\s=\\s")[[1]][2], "}", sep = "")
if (length(which(positions.PotentialSteps == 1)) > 1) {
for (i in 2:length(which(positions.PotentialSteps == 1))) {
PotentialSteps <-
paste(PotentialSteps,
paste("\\num{", strsplit(chifile[which(positions.PotentialSteps == 1)],
"\\s=\\s")[[i]][2], "}", sep = ""), sep = ", ")
}
}
ff$PotentialSteps <- PotentialSteps
# Time steps
TimeSteps <- ""
positions.TimeSteps <- regexpr("^T\\d+\\s\\(s\\)", chifile)
TimeSteps <- paste("\\num{", strsplit(chifile[which(positions.TimeSteps == 1)],
"\\s=\\s")[[1]][2], "}", sep = "")
if (length(which(positions.TimeSteps == 1)) > 1) {
for (i in 2:length(which(positions.TimeSteps == 1))) {
TimeSteps <-
paste(TimeSteps,
paste("\\num{", strsplit(chifile[which(positions.TimeSteps == 1)],
"\\s=\\s")[[i]][2], "}", sep = ""), sep = ", ")
}
}
ff$TimeSteps <- TimeSteps
# Cycles
position.Cycles <- regexpr("^Cycle", chifile)
Cycles <- as.numeric(strsplit(chifile[which(position.Cycles == 1)], "\\s=\\s")[[1]][2])
ff$Cycles <- Cycles
# Sample interval (s)
position.SampleInterval <- regexpr("^Sample\\sInterval\\s\\(s\\)", chifile)
SampleInterval <- as.numeric(strsplit(chifile[which(position.SampleInterval == 1)], "\\s=\\s")[[1]][2])
ff$SampleInterval <- SampleInterval
# Quiet Time (s)
position.QuietTime <- regexpr("^Quiet\\sTime\\s\\(sec\\)", chifile)
QuietTime <- as.numeric(strsplit(chifile[which(position.QuietTime == 1)], "\\s=\\s")[[1]][2])
ff$QuietTime <- QuietTime
# Sensitivity (A/V)
position.Sensitivity <- regexpr("^Sensitivity\\s\\(A/V\\)", chifile)
Sensitivity <- as.numeric(strsplit(chifile[which(position.Sensitivity == 1)], "\\s=\\s")[[1]][2])
ff$Sensitivity <- Sensitivity
#
return(ff)
}