Weight Unit Converter in R-CodePudding

Is there a way to create a function in r which takes in the value to convert, the input weight unit and output weight unit?

converter<-fuction(value_in, unit_in, unit_out){
     #some code
     return value_out
}

For example i want to convert 1 kg to grams. So i would write Something like this:

if (value_in=="kg" and value_out=="grams"){
   return (value/1000)
}

But how do i write this if i have like over ten weight units (for example kg, st, ls, oz etc.). Do i have to write an if else statement for every possible opportunity or is there a simpler way? I thought about the switch statement but not sure how to use two expressions here.

CodePudding user response：

We can create a function containing an index with all values corresponding to a standardized unit. I suggest we use grams as the standard unit. A Kg would correspond to a correction rate of 1000.

converter <- function(unit_in, unit_out, value){
    index <- c(kg=1000, g=1)
    output <- value * index[unit_in] / index[unit_out]
    names(output) <- NULL
    output
}

converter('kg', 'g', 5)

[1] 5000

CodePudding user response：

You can use recode() to do the conversions:

library(dplyr)

conv_key <- c("kilogram" = 1000, "gram" = 1,  "milligram" = 0.0001)

conv <- function(value, unit_in, unit_out) {
  
  input <- value*recode(unit_in, !!!conv_key)
  
  input/recode(unit_out, !!!conv_key)
}

conv(2, "kilogram", "gram")

# [1] 2000

CodePudding user response：

Rolling your own set and method of doing unit conversions could be fun but also time-consuming and potentially error-prone. You might consider using the units package which can perform a wide range of unit conversions:

library(units)

some_weight <- set_units(1, kg)
some_weight
# 1 [kg]
units(some_weight) <- make_units(g)
some_weight
# 1000 [g]