Can spread() in tidyr spread across multiple value?

Question

I am using the iris data set, first, I did some manipulation with that data set and make it into the following form

D1 = iris[,c(1,2,5)]
D2 = iris[,c(3,4,5)]
colnames(D1)[1:2] = c('Length','Width')
colnames(D2)[1:2] = c('Length','Width')
D1 = D1 %>% mutate(Part = 'Sepal')
D2 = D2 %>% mutate(Part = 'Petal')
D = rbind(D2,D1)

which looks like

Species  Part Length Width
1  setosa Petal    1.4   0.2
2  setosa Petal    1.4   0.2
3  setosa Petal    1.3   0.2
4  setosa Petal    1.5   0.2
5  setosa Petal    1.4   0.2
6  setosa Petal    1.7   0.4

I want to use the spread() function in the tidyr to make the data set look like the following format eventually

Measure Part setosa versicolor virginica
Length  Petal 1.4     4.7        6.0

What I did is the following:

D4 = D %>% gather(Measure,value,3:4)

which gives

Species  Part Measure value
1  setosa Petal  Length   1.4
2  setosa Petal  Length   1.4
3  setosa Petal  Length   1.3
4  setosa Petal  Length   1.5
5  setosa Petal  Length   1.4
6  setosa Petal  Length   1.7

I've tried to add a row number to 'D4', since I found that sometimes, the spread() function will result into some error as discussed here. I don't know if there is a neat way to use spread() to achieve this goal.

akrun akrun · Accepted Answer · 2017-02-08T03:42:57

We need to create a sequence variable by group and then spread

library(tidyverse)
D %>% 
   gather(Measure, value, Length, Width) %>% 
   group_by(Species, Part, Measure) %>%
   mutate(i1 = row_number()) %>% 
   spread(Species, value) %>%
   select(-i1)
#    Part Measure setosa versicolor virginica
#*  <chr>   <chr>  <dbl>      <dbl>     <dbl>
#1  Petal  Length    1.4        4.7       6.0
#2  Petal  Length    1.4        4.5       5.1
#3  Petal  Length    1.3        4.9       5.9
#4  Petal  Length    1.5        4.0       5.6
#5  Petal  Length    1.4        4.6       5.8
#6  Petal  Length    1.7        4.5       6.6
#7  Petal  Length    1.4        4.7       4.5
#8  Petal  Length    1.5        3.3       6.3
#9  Petal  Length    1.4        4.6       5.8
#10 Petal  Length    1.5        3.9       6.1
# ... with 190 more rows

Can spread() in tidyr spread across multiple value?

1 Answers