Floni - 1 year ago 71
R Question

# R: find the closest observation to averages

I have a table with description statistics (means for a, b and c) per type

``````### stats
type <- c("a","b","c","d","e","f","g","h","i","j","k","l")
mean_a <- c(0,1,1,0,2,2,0,4,4,0,5,5)
mean_b<- c(4,7,8,0,3,10,5,4,7,0,1,6)
mean_c<- c(1,2,0,3,4,5,1,24,3,0,4,5)
stats <- data.frame(type, mean_a, mean_b, mean_c)
``````

I have a dataset with observations of specimen for the parameters a, b and c.
Each of the specimens have a particular type

``````# data
Id <- c("ted","bert","test","john","elf","fea","goul","houl","ili","jok","ko","lol")
type <- c("a","a","b","d","f","f","c","d","a","b","k","l")
a <- c(2,1,3,2,1,2,0,1,2,1,5,5)
b<- c(1,3,4,7,5,4,5,6,5,0,1,6)
c<- c(3,5,2,6,8,5,1,5,3,1,6,6)
data <- data.frame(Id, type, a, b, c )
``````

Following these two tables, I would like to get from
`data`
the specimen the most representative of the type following the statistics in
`stats`
.
By most representative, I would like to get the one with the closest values for a, b and c to their respectives averages.

I can not find ideas on internet following 3 averages( a, b and c). Help is welcome! Ouput wanted (but not sure if ted, test and john are the closest to the averages for the types a, b and c):

``````# output wanted
Id <- c("ted","test","john")
type <- c("a","b","c")
a <- c(2,3,2)
b<- c(1,4,7)
c<- c(3,2,6)
data2 <- data.frame(Id, type, a, b, c )
``````

The "most representative" as you mention on its own is very vague but here is an attempt which finds the difference between the values from `data` and the mean_values from `stats` and keeps the one with the lowest average. Since I joined the data frames before hand, you can use the `select()` function at the end of the code and modify (keep/drop variables) accordingly.

``````library(dplyr)
df1 <- merge(data1, stats, by = 'type')
df1 %>%
mutate(new = abs(rowMeans(mapply(`-`, df1[,(3:5)], df1[,(6:8)])))) %>%
group_by(type) %>%
filter(new == min(new)) %>%
select(-new)

#Source: local data frame [7 x 8]
#Groups: type [7]

#    type     Id     a     b     c mean_a mean_b mean_c
#  <fctr> <fctr> <dbl> <dbl> <dbl>  <dbl>  <dbl>  <dbl>
#1      a    ted     2     1     3      0      4      1
#2      b   test     3     4     2      1      7      2
#3      c   goul     0     5     1      1      8      0
#4      d   houl     1     6     5      0      0      3
#5      f    elf     1     5     8      2     10      5
#6      k     ko     5     1     6      5      1      4
#7      l    lol     5     6     6      5      6      5
``````
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