Unit conversions

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Question

How to convert data from one unit to another in R?

Answer

We need conversion factors, which are listed below, and a code that does the actual conversion.

Unit conversions(-)

Obs	From	To	Result	Description
1	MWh	MJ	3600	1 MWh = 1 MWh * 3600 s/h = 3600 MWs = 3600 MJ
2	toe	MJ	35000	1 toe = 1000 kgoe = 1000 kg * 35 MJ/kg = 35000 MJ

+ Show code- Hide code ############# convert.units: a function that converts units from one to another, if possible. # value = a numeric vector with values to be converted # fromunit = a numeric vector with the current units # tounit = a string for the new units to be used. Must be found from the To column from the table in [[Unit conversions]]. # expo = exponent for the conversion. If -1 converts the inverse, i.e. backward, or a unit that is in the denominator of a compiled unit. convert.units <- function(value, fromunit = NULL, tounit = NULL, expo = 1) { data <- fetch("Op_en5475") print(data) out <- merge(fromunit, data, by.y = "From") print(out) out <- out[out$To == tounit, ] print(out) out <- merge(value, out, all.x = TRUE) print(out) out <- out$value * out$Factor^expo print(out) return(out) } cat("Starting model\n") a <- data.frame(Unit = "MW", Result = 1) convert.units(1, "MWh", "MJ") temp <- setGeneric("convert.units") temp <- setMethod( f = "convert.units", signature = signature(data = "ovariable"), definition = function(x, tounit = NULL) { x@sample[c("Unit", "Result")] <- convert.units(x@sample$Result, x@sample$Unit, tounit) return(x) } )

⇤--#: . The code does not work because the merges and combinations do not match. Values should have some row identifier that makes it possible to link a row in value to the right row in out. Should value and fromunit be two columns in a data.frame? --Jouni 11:29, 25 January 2012 (EET) (type: truth; paradigms: science: attack)