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# SETMETHOD CONVERT.UNITS####################################################3
############# convert.units: a function that converts units from one to another, if possible.
# x = a numeric vector with values to be converted
# tounit = a character vector of the new units to be used. Must be found from the To column from the table in [[Unit conversions]].
# fromunit = a character vector or factor with the current units
convert.units <- function(x, tounit = c("kg", "s", "m", "m3", "J", "W", "A", "V", "C", "N", "Pa", "Hz", "mol"), fromunit = NULL) {
if(is.null(tounit)) {tounit <- c("kg", "s", "m", "m3", "J", "W", "A", "V", "C", "N", "Pa", "Hz", "mol")}
if(is.null(fromunit)) { # Do nothing if from-units are not defined.
out <- data.frame(Unit = fromunit, Result = x)
} else {
conversions <- fetch("Op_en5475") # Set up a full unit conversion table.
conversions$Result <- as.numeric(conversions$Result)
colnames(conversions)[colnames(conversions) == "type"] <- "Type"
prefixes <- conversions[conversions$Type == "Prefix", ] # Combine all prefixes with all units in From column.
colnames(prefixes) <- paste("Prefix.", colnames(prefixes), sep = "")
conversions <- merge(prefixes, conversions[conversions$Type == "Unit", ])
conversions$From <- paste(conversions$Prefix.From, conversions$From, sep = "")
conversions$Result <- conversions$Result * conversions$Prefix.Result
conversions <- conversions[c("From", "To", "Result")]
conversions <- merge(conversions, conversions, by = "To") # Create all possible from-to pairs.
conversions$Result <- conversions$Result.x / conversions$Result.y
conversions <- unique(conversions[c("From.x", "From.y", "Result")])
colnames(conversions) <- c("From", "To", "Result")
coefficients <- data.frame()
for(i in levels(as.factor(fromunit))) { # Look through each different "From" unit in the data.
coefficient <- 1
outto <- ""
for(j in strsplit(i, split = " ")[[1]]) { # Look though each part of a composite unit.
if(gsub("^/", "", j) != j) { # If unit is in denominator, use inverse.
j <- gsub("^/", "", j)
exponent <- -1
slash <- "/"
} else {
exponent <- 1
slash <- ""
}
conversions.j <- merge(conversions, j, by.x = "From", by.y = "y")
conversions.j <- conversions.j[conversions.j$To %in% tounit, ]
if(nrow(conversions.j) > 0) {
coefficient <- coefficient * conversions.j$Result^exponent
outto <- paste(outto, " ", slash, conversions.j$To, sep = "")
}
}
coefficients <- rbind(coefficients, data.frame(
From = i,
To = gsub("^ ", "", outto),
Result = coefficient
))
}
# Combine coefficients with data.
out <- merge(fromunit, coefficients, by.x = "x", by.y = "From", sort = FALSE)
out <- data.frame(Unit = out$To, Result = x * out$Result)
}
return(out)
}
temp <- setGeneric("convert.units")
temp <- setMethod(
f = "convert.units",
signature = signature(x = "ovariable"),
definition = function(x, tounit)
{
if("Unit" %in% colnames(x@output) & !is.null(tounit)) {
x@output[c("Unit", "Result")] <- convert.units(x = x@output$Result, tounit = tounit, fromunit = x@output$Unit, expo = expo)
}
return(x)
}
)
temp <- setMethod(
f = "convert.units",
signature = signature(x = "data.frame"),
definition = function(x, tounit = NULL)
{
if("Unit" %in% colnames(x) & "Result" %in% colnames(x) & !is.null(tounit)) {
x[c("Unit", "Result")] <- convert.units(x = x$Result, tounit = tounit, fromunit = x$Unit, expo = expo)
}
return(x)
}
)
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