问题
I want to sort this matrix row-wise to descending order
> set.seed(123); a <- matrix(rbinom(100,10,0.3),ncol=10)
[,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8] [,9] [,10]
[1,] 2 6 5 6 1 1 4 4 2 1
[2,] 4 3 4 5 3 3 1 3 4 4
[3,] 3 4 3 4 3 4 3 4 3 2
[4,] 5 3 7 4 2 1 2 0 4 4
[5,] 5 1 4 0 2 3 4 3 1 2
[6,] 1 5 4 3 1 2 3 2 3 2
[7,] 3 2 3 4 2 1 4 2 6 4
[8,] 5 1 3 2 3 4 4 3 5 1
[9,] 3 2 2 2 2 5 4 2 5 3
[10,] 3 6 1 2 5 2 3 1 2 3
but
> do.call(order,as.list(a[1,],a[2,]))
[1] 1
How can you sort the matrix with the do.call and order?
Edit. Fixed above matrix to conform with the above code.
回答1:
Two alternatives:
# Jaap
do.call(rbind, lapply(split(a, row(a)), sort, decreasing = TRUE))
# adaption of lmo's solution in the comments
for(i in 1:nrow(a)) a[i,] <- a[i,][order(a[i,], decreasing = TRUE)]
gives:
[,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8] [,9] [,10]
1 6 6 5 4 4 2 2 1 1 1
2 5 4 4 4 4 3 3 3 3 1
3 4 4 4 4 3 3 3 3 3 2
4 7 5 4 4 4 3 2 2 1 0
5 5 4 4 3 3 2 2 1 1 0
6 5 4 3 3 3 2 2 2 1 1
7 6 4 4 4 3 3 2 2 2 1
8 5 5 4 4 3 3 3 2 1 1
9 5 5 4 3 3 2 2 2 2 2
10 6 5 3 3 3 2 2 2 1 1
A benchmark with:
library(microbenchmark)
microbenchmark(dc.lapply.sort = do.call(rbind, lapply(split(a, row(a)), sort, decreasing = TRUE)),
t.apply.sort = t(apply(a, 1, sort, decreasing = TRUE)),
for.order = for(i in 1:nrow(a)) a[i,] <- a[i,][order(a[i,], decreasing = TRUE)],
for.sort = for(i in 1:nrow(a)) a[i,] <- sort(a[i,], decreasing = TRUE),
for.sort.list = for(x in seq_len(nrow(a))) a[x,] <- a[x,][sort.list(a[x,], decreasing = TRUE, method="radix")])
gives:
Unit: microseconds
expr min lq mean median uq max neval cld
dc.lapply.sort 189.811 206.5890 222.52223 217.8070 228.0905 332.034 100 c
t.apply.sort 185.474 200.4515 212.59608 210.4930 220.0025 286.288 100 bc
for.order 82.631 91.1860 98.66552 97.8475 102.9680 176.666 100 a
for.sort 167.939 187.5025 192.90728 192.1195 198.8690 256.494 100 b
for.sort.list 187.617 206.4475 230.82960 215.7060 221.6115 1541.343 100 c
It should be noted however that benchmarks are only meaningful on larger datasets, so:
set.seed(123)
a <- matrix(rbinom(10e5, 10, 0.3), ncol = 10)
microbenchmark(dc.lapply.sort = do.call(rbind, lapply(split(a, row(a)), sort, decreasing = TRUE)),
t.apply.sort = t(apply(a, 1, sort, decreasing = TRUE)),
for.order = for(i in 1:nrow(a)) a[i,] <- a[i,][order(a[i,], decreasing = TRUE)],
for.sort = for(i in 1:nrow(a)) a[i,] <- sort(a[i,], decreasing = TRUE),
for.sort.list = for(x in seq_len(nrow(a))) a[x,] <- a[x,][sort.list(a[x,], decreasing = TRUE, method="radix")],
times = 10)
gives:
Unit: seconds
expr min lq mean median uq max neval cld
dc.lapply.sort 6.790179 6.924036 7.036330 7.013996 7.121343 7.351729 10 d
t.apply.sort 5.032052 5.057022 5.151560 5.081459 5.177159 5.538416 10 c
for.order 1.368351 1.463285 1.514652 1.471467 1.583873 1.736544 10 a
for.sort 5.028314 5.102993 5.317597 5.154104 5.348614 6.123278 10 c
for.sort.list 2.417857 2.464817 2.573294 2.519408 2.726118 2.815964 10 b
Conclusion: the for-loop in combination with order is still the fastest solution.
Using the order2 and sort2 functions of the grr-package can give a further improvement in speed. Comparing them with the fastest solution from above:
set.seed(123)
a <- matrix(rbinom(10e5, 10, 0.3), ncol = 10)
microbenchmark(for.order = for(i in 1:nrow(a)) a[i,] <- a[i,][order(a[i,], decreasing = TRUE)],
for.order2 = for(i in 1:nrow(a)) a[i,] <- a[i,][rev(grr::order2(a[i,]))],
for.sort2 = for(i in 1:nrow(a)) a[i,] <- rev(grr::sort2(a[i,])),
times = 10)
giving:
Unit: milliseconds
expr min lq mean median uq max neval cld
for.order 1243.8140 1263.4423 1316.4662 1305.1823 1378.5836 1404.251 10 c
for.order2 956.1536 962.8226 1110.1778 1090.9984 1233.4241 1368.416 10 b
for.sort2 830.1887 843.6765 920.5668 847.1601 972.8703 1144.135 10 a
回答2:
t(apply(a, 1, sort, decreasing = TRUE)) gives:
# [,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8] [,9] [,10]
# [1,] 6 6 5 4 4 2 2 1 1 1
# [2,] 5 4 4 4 4 3 3 3 3 1
# [3,] 4 4 4 4 3 3 3 3 3 2
# [4,] 7 5 4 4 4 3 2 2 1 0
# [5,] 5 4 4 3 3 2 2 1 1 0
# [6,] 5 4 3 3 3 2 2 2 1 1
# [7,] 6 4 4 4 3 3 2 2 2 1
# [8,] 5 5 4 4 3 3 3 2 1 1
# [9,] 5 5 4 3 3 2 2 2 2 2
# [10,] 6 5 3 3 3 2 2 2 1 1
回答3:
I did also microbenchmarking and it seems that the order solutions win :)
> microbenchmark(jaap1 = do.call(rbind, lapply(split(a, row(a)), sort, decreasing = TRUE)),
+ apom = t(apply(a, 1, sort, decreasing = TRUE)),
+ jaap2 = for(i in 1:nrow(a)) a[i,] <- a[i,][order(a[i,], decreasing = TRUE)],
+ jaap3 = for(i in 1:nrow(a)) a[i,] <- sort(a[i,], decreasing = TRUE),
+ alpha = t(apply(a, 1, function(x) order(x, decreasing = T))),
+ times = 1000L)
Unit: microseconds
expr min lq mean median uq max neval
jaap1 318.193 364.6125 404.3224 389.5845 417.6405 1422.087 1000
apom 276.764 340.2740 389.1302 364.9650 398.3680 2854.710 1000
jaap2 121.332 158.4845 189.5616 182.2070 202.2390 1170.602 1000
jaap3 247.387 309.2445 351.6959 332.2710 365.3640 1361.720 1000
alpha 139.244 178.7460 209.6122 202.8580 226.7585 1092.301 1000
来源：https://stackoverflow.com/questions/41594138/do-call-and-order-to-sort-each-row-to-descending-order-of-a-matrix