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133 lines
4.3 KiB
R
133 lines
4.3 KiB
R
# common.R
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# General-purpose functions
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# Taha Ahmed, Jan 2011
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# CONTENTS
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# >>>> ConvertRefPot
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# >>>> Celsius2Kelvin
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# >>>> Kelvin2Celsius
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# >>>> as.radians
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# >>>> as.degrees
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# >>>> molarity2mass
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##################################################
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################# ConvertRefPot ##################
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##################################################
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ConvertRefPot <- function(argpotential, argrefscale, valuerefscale) {
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# Converts from some reference potential scale into another
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# SHE: standard hydrogen electrode scale
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# Ag/AgCl: silver silver-chloride electrode scale
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# SCE: standard calomel scale
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#
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##### Add more reference electrodes here >>
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refpotatSHEzero <- c( 0, -0.21, -0.24, 3)
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refrownames <- c( "SHE", "Ag/AgCl", "SCE", "Li/Li+")
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refcolnames <- c("SHE0", "AgCl0", "SCE0", "Li0")
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##### Add more reference electrodes here <<
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#
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SHE0 <- data.frame(matrix(refpotatSHEzero, ncol=length(refpotatSHEzero), byrow=T))
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refpotmtx <- matrix(NA, length(SHE0), length(SHE0))
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refpotmtx[,1] <- matrix(as.matrix(SHE0), ncol=1, byrow=T)
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for (c in 2:length(SHE0)) {
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# loop over columns (except the first)
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for (r in 1:length(SHE0)) {
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# loop over rows
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refpotmtx[r, c] <- refpotmtx[r, 1] - refpotmtx[c, 1]
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}
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}
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refpotdf <- as.data.frame(refpotmtx)
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names(refpotdf) <- refcolnames
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row.names(refpotdf) <- refrownames
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## So far we have made a matrix of all the possible combinations,
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## given the vector refpotatSHEzero. The matrix is not strictly necessary,
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## but it may prove useful later. It does.
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#
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# Match argrefscale to the refrownames
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argmatch <- match(argrefscale, refrownames, nomatch = 0)
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# Match valuerefscale to the refrownames
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valuematch <- match(valuerefscale, refrownames, nomatch = 0)
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# We simply assume that the match was well-behaved
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valuepotential <- argpotential + refpotdf[valuematch, argmatch]
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# Check that arg and value electrodes are within bounds for a match
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if (argmatch == 0 || valuematch == 0) {
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# No match
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# Perform suitable action
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message("Arg out of bounds in call to ConvertRefPot")
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valuepotential <- NA
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}
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return(valuepotential)
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}
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##################################################
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############### Celsius2Kelvin ###################
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##################################################
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Celsius2Kelvin <- function(Celsius) {
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# Converts temperature from Celsius to Kelvin
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#
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# Check and correct for values below -273.15
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if (Celsius < -273.15) {
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# If Celsis is less than absolute zero, set it to absolute zero
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Celsius <- -273.15
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}
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Kelvin <- Celsius + 273.15
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return(Kelvin)
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}
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##################################################
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############### Kelvin2Celsius ###################
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##################################################
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Kelvin2Celsius <- function(Kelvin) {
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# Converts temperature from Kelvin to Celsius
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#
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# Check and correct for negative values
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if (Kelvin < 0) {
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# If Kelvin is less than zero, set it to zero
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Kelvin <- 0
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}
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Celsius <- Kelvin - 273.15
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return(Celsius)
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}
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##################################################
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################# as.radians #####################
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##################################################
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as.radians <- function(degrees) {
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# Converts from degrees to radians
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radians <- degrees * (pi / 180)
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return(radians)
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}
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##################################################
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################# as.degrees #####################
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##################################################
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as.degrees <- function(radians) {
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# Converts from radians to degrees
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degrees <- radians * (180 / pi)
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return(degrees)
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}
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##################################################
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############### molarity2mass ####################
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##################################################
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molarity2mass <- function(formulamass, volume, molarity) {
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# Calculates the required mass of
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# the substance to be dissolved.
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# ARGS: formulamass - formula mass of the substance (in gram per mole)
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# volume - volume of the final solution (in liters)
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# molarity - molarity (in moles per liter)
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# VALUE: mass of substance (in grams)
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#
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mass <- formulamass * volume * molarity
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# Unit check:
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# [g * mol-1] * [liter] * [mole * liter-1] = [g]
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return(mass)
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}
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