Using Min and max function inside a function

Question

I have created a function which uses 2 variables to do grouping and uses third variable to create min and max for each groups. But the min and max function gives wrong output. It gives the minimum and maximum for entire dataset and not for each group.

myfunction= function(x,a,b,column) {
  temp=group_by(x,x[[a]],x[[b]])
   Score=summarise(temp,Totals=n(),Mnscore=min(x[[c]]),Mxscore=max(x[[c]]))
 return(Score)
}

myfunction(dataset,"a","b","c")


Actual Results:
a b Totals  Min Max
1 1  10     15  50
1 2  20     15  50
1 3  30     15  50

Expected results:
a b Totals  Min Max
1 1  10     20  48
1 2  20     21  49
1 3  30     15  50

you need to learn about lazy evaluations and quasi quotations in R. — Onyambu
– Onyambu, Commented Oct 11, 2019 at 18:23

Onyambu · Accepted Answer · 2019-10-11 18:43:11Z

1

to write a function, you could do the following:

library(tidyverse)
myfunction= function(x,a,b,column) 
  {
  column <- enquo(column)
  vars <- enquos(a,b)
  x %>% 
    group_by(!!!vars) %>% 
    summarise(Totals=n(),Mnscore=min(!!c),Mxscore=max(!!column))
}

then call this inputing a,b,c as symbols and not characters

myfunction(dataset,a,b,column)

edited Oct 11, 2019 at 18:43

answered Oct 11, 2019 at 18:34

Onyambu

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2 Comments

Artem Sokolov Over a year ago

rlang 0.4.0 added a new curly-curly operator, which is effectively a shortcut for !!enquo(). So, now you can just do ... %>% summarize( Totals=n(), Mnscore = min({{column}}), Mxscore=max({{column}}) ). (Also, it is generally not advisable to use c as a variable name because of its conflict with the built-in c().)

Onyambu Over a year ago

@ArtemSokolov true its not advisable to use c.

J.P. Le Cavalier · Accepted Answer · 2019-10-11 18:32:09Z

1

You can use the data.table package if you want a very effective way to solve your problem. Try the following minimal reproducible example.

library(data.table)
set.seed(20191011L)

data <- data.table(
  V1 = letters[sample(3, 20, TRUE)],
  V2 = letters[sample(3, 20, TRUE)],
  V3 = runif(20)
)

fun <- function(data, groups, target){

  data[, .(min=min(get(target)), max=max(get(target))), mget(groups)]

}

fun(data, c("V1", "V2"), "V3")

##     V1 V2        min       max
##  1:  b  c 0.20653948 0.4618063
##  2:  a  a 0.09560888 0.3347064
##  3:  b  b 0.75071480 0.7507148
##  4:  c  a 0.66410519 0.8258410
##  5:  c  c 0.01303751 0.7635212
##  6:  a  b 0.04770186 0.6332439
##  7:  b  a 0.25069813 0.9008885

edited Oct 11, 2019 at 18:32

answered Oct 11, 2019 at 18:18

J.P. Le Cavalier

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4 Comments

unknown Over a year ago

I want to create as a function since I have to use that function multiple times.

J.P. Le Cavalier Over a year ago

Sorry, did not saw you asked for a function. I edit my answer to implement it as a function.

unknown Over a year ago

I am getting this error : Error in .(min = min(get(target)), max = max(get(target))) : could not find function "."

J.P. Le Cavalier Over a year ago

Make sure your data is a data.table and not a data.frame

makeshift-programmer · Accepted Answer · 2019-10-11 18:15:19Z

0

Try this:

require(dplyr)

result = dataset %>% 
  dplyr::group_by(a,b) %>% 
  dplyr::summarise(Totals = n(),
                   Mnscore = min(c),
                   Mxscore = max(c))

Let me know if it works.

answered Oct 11, 2019 at 18:15

makeshift-programmer

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3 Comments

Onyambu Over a year ago

how is this a function?

makeshift-programmer Over a year ago

@Onyambu, it's not but OP does not necessarily need a function here.

unknown Over a year ago

I want to create as a function since I have to use that function multiple times.

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