CODEWITHSUNDEEP
r
Matthew
Matthew

Reputation: 79

identify the first column with a non-zero value for each row in a data frame

I have a data frame :

str(HSCtc_all_maxcols)
'data.frame':   12308 obs. of  11 variables:
 $ AGI   : Factor w/ 27747 levels "AT1G01010","AT1G01020",..: 1 6 7 8 12 14 17 18 19 20 ...
 $ k2.5m : num  0 0 0 0 0 0 0 0 0 0 ...
 $ k5m   : num  0 -0.38 0 0 0 0 0 0 0 0 ...
 $ k10m  : num  0 -0.6 0 0 0 -0.27 0 0 0 0 ...
 $ k15m  : num  0 -0.6 0 0 0 0 0 0 0 0 ...
 $ k20m  : num  0 0.33 0 -0.23 0 0.85 0 0.46 0 0 ...
 $ k30m  : num  0 0 -0.69 0 0.49 1 0 1.03 0 -1.17 ...
 $ k1h   : num  1.12 0 -1.46 -0.42 0.88 1.15 0 1.62 0 -1.3 ...
 $ k3h   : num  1.92 -0.61 -0.9 -1.55 1.67 -0.57 -0.6 1.08 -0.91 0 ...
 $ k30h  : num  0.62 0 0 0 0.26 0.2 -0.32 0 1.13 0 ...
 $ maxcol: chr  "k9h" "k9h" "k9h" "k2.5m" ...

head(HSCtc_all_maxcols)
        AGI k2.5m   k5m  k10m k15m  k20m  k30m   k1h   k3h k30h maxcol
1 AT1G01010     0  0.00  0.00  0.0  0.00  0.00  1.12  1.92 0.62    k9h
2 AT1G01060     0 -0.38 -0.60 -0.6  0.33  0.00  0.00 -0.61   0.00    k9h
3 AT1G01070     0  0.00  0.00  0.0  0.00 -0.69 -1.46 -0.90  0.00    k9h
4 AT1G01080     0  0.00  0.00  0.0 -0.23  0.00 -0.42 -1.55  0.00  k2.5m
5 AT1G01120     0  0.00  0.00  0.0  0.00  0.49  0.88  1.67   0.26    k3h
6 AT1G01140     0  0.00 -0.27  0.0  0.85  1.00  1.15 -0.57  0.20    k1h

For each row in this data frame, I would like to identify the column name which has the first non-zero value (going from left to right). For example, in the above, for row 1 the column name with the first non-zero value is k1h. For row 2 it is k5m.

I have already written code to identify for each row the name of column with the highest value and this appears as the last value for each row in the column named maxcol. The code to do this was:

HSCtc_all_maxcols <- HSCtc_all %>% mutate(maxcol = names(HSCtc_all[2:18])[apply(HSCtc_all[,2:18],1,which.max)])

I would like to add another column to the data frame that identifies for each row the name of column with the first non-zero value.

For example: 

head(HSCtc_all_maxcols)
        AGI k2.5m   k5m  k10m k15m  k20m  k30m   k1h   k3h  k30h maxcol fcol
1 AT1G01010     0  0.00  0.00  0.0  0.00  0.00  1.12  1.92   0.62   k9h   k1h
2 AT1G01060     0 -0.38 -0.60 -0.6  0.33  0.00  0.00 -0.61   0.00   k9h   k5m
3 AT1G01070     0  0.00  0.00  0.0  0.00 -0.69 -1.46 -0.90   0.00   k9h  k30m
4 AT1G01080     0  0.00  0.00  0.0 -0.23  0.00 -0.42 -1.55  0.00 k2.5m   k20m
5 AT1G01120     0  0.00  0.00  0.0  0.00  0.49  0.88  1.67   0.26   k3h k30m
6 AT1G01140     0  0.00 -0.27  0.0  0.85  1.00  1.15 -0.57  0.20    k1h k10m

Upvotes: 0

Views: 1008

Answers (2)

Ronak Shah
Ronak Shah

Reputation: 389125

We could use apply row-wise with which.max to get index of first non-zero value in row and then use that index to subset the names

names(df[-1])[apply(df[-1] != 0, 1, which.max)]
#[1] "k1h"  "k5m"  "k30m" "k20m" "k30m" "k10m"

data

df <- structure(list(AGI = structure(1:6, .Label = c("AT1G01010", "AT1G01060", 
"AT1G01070", "AT1G01080", "AT1G01120", "AT1G01140"), class = "factor"), 
k2.5m = c(0L, 0L, 0L, 0L, 0L, 0L), k5m = c(0, -0.38, 0, 0, 
0, 0), k10m = c(0, -0.6, 0, 0, 0, -0.27), k15m = c(0, -0.6, 
0, 0, 0, 0), k20m = c(0, 0.33, 0, -0.23, 0, 0.85), k30m = c(0, 
0, -0.69, 0, 0.49, 1), k1h = c(1.12, 0, -1.46, -0.42, 0.88, 
1.15), k3h = c(1.92, -0.61, -0.9, -1.55, 1.67, -0.57), k30h = c(0.62, 
0, 0, 0, 0.26, 0.2), maxcol = structure(c(4L, 4L, 4L, 2L, 
3L, 1L), .Label = c("k1h", "k2.5m", "k3h", "k9h"), class = "factor")), 
class = "data.frame", row.names = c("1", "2", "3", "4", "5", "6"))

Upvotes: 1

Shree
Shree

Reputation: 11150

Here's a way in base R using max.col() -

names(HSCtc_all[2:18])[max.col(HSCtc_all[2:18] != 0, ties.method = "first")]

Upvotes: 2

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