For loop and unexpected results - r

Question

I'm trying to write a for loop but I couldn't finish it. If I ran them out of for loop it works well but I didn't understand where is the problem.
output100 <- structure(list(row = c(1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L,
2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L), col = c(17L, 17L, 17L,
17L, 17L, 17L, 17L, 17L, 17L, 17L, 16L, 16L, 16L, 16L, 16L, 16L,
16L, 16L, 16L, 16L), cell = c(0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L,
0L, 0L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L), xcoord = c(783750L,
783750L, 783750L, 783750L, 783750L, 783750L, 783750L, 783750L,
783750L, 783750L, 783725L, 783725L, 783725L, 783725L, 783725L,
783725L, 783725L, 783725L, 783725L, 783725L), ycoord = c(187050L,
187050L, 187050L, 187050L, 187050L, 187050L, 187050L, 187050L,
187050L, 187050L, 187025L, 187025L, 187025L, 187025L, 187025L,
187025L, 187025L, 187025L, 187025L, 187025L), species = structure(c(1L,
1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L,
1L, 1L, 1L), .Label = c("abiealba", "alnuviri", "larideci", "piceabie",
"pinucemb", "pinusilv", "popunigr", "poputrem", "salicapr", "sorbaucu"
), class = "factor"), age = c(590L, 250L, 230L, 210L, 200L, 190L,
180L, 110L, 100L, 90L, 720L, 320L, 300L, 230L, 170L, 160L, 150L,
140L, 130L, 80L), biomass = c(6.3836, 1.2988, 0.9683, 0.6574,
0.5083, 0.3398, 0.2163, 0.0863, 0.0591, 0.0418, 6.6135, 1.7666,
1.214, 0.7032, 0.3422, 0.2571, 0.1601, 0.0846, 0.0592, 0.0323
), stems = c(1L, 1L, 3L, 1L, 2L, 6L, 5L, 8L, 3L, 5L, 1L, 3L,
1L, 1L, 2L, 5L, 7L, 4L, 6L, 5L), slowGrowth = c(0L, 0L, 0L, 0L,
0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L
), DBH = c(104.9563, 50.7341, 44.7226, 37.9815, 34.1311, 28.9447,
24.1329, 16.8379, 14.5727, 12.7875, 106.7731, 58.0343, 49.2757,
39.0663, 29.027, 25.8599, 21.4205, 16.7129, 14.5803, 11.6105),
height = c(45.999, 30.659, 28.1508, 25.0823, 23.1987, 20.5,
17.8196, 13.4049, 11.9423, 10.7572, 46.3418, 33.4408, 30.0693,
25.5954, 20.5444, 18.802, 16.2293, 13.3254, 11.9472, 9.96
), availableLight = c(0.8129, 0.4994, 0.3701, 0.2541, 0.217,
0.1588, 0.102, 0.075, 0.06, 0.0545, 0.8083, 0.4101, 0.2332,
0.196, 0.1694, 0.1347, 0.0941, 0.0702, 0.0602, 0.0519), light_rf = c(0.9832,
0.8951, 0.8029, 0.6577, 0.592, 0.463, 0.2972, 0.2003, 0.1407,
0.1174, 0.9826, 0.8371, 0.6213, 0.5487, 0.4885, 0.3973, 0.2696,
0.181, 0.1409, 0.1056), LeafArea = c(5.9777, 5.9777, 5.9777,
5.9777, 5.9777, 5.9777, 5.9777, 5.9777, 5.9777, 5.9777, 6.218,
6.218, 6.218, 6.218, 6.218, 6.218, 6.218, 6.218, 6.218, 6.218
), nitorgen_rf = c(0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0), droughtIndex = c(0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0), moisture_rf = c(1,
1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1),
degreeDay_rf = c(0.4405, 0.4405, 0.4405, 0.4405, 0.4405,
0.4405, 0.4405, 0.4405, 0.4405, 0.4405, 0.4405, 0.4405, 0.4405,
0.4405, 0.4405, 0.4405, 0.4405, 0.4405, 0.4405, 0.4405),
foliageWght = c(0.1471, 0.0473, 0.0389, 0.0301, 0.0255, 0.0197,
0.0149, 0.0085, 0.0068, 0.0055, 0.1511, 0.0584, 0.0452, 0.0315,
0.0198, 0.0165, 0.0123, 0.0084, 0.0068, 0.0047), twigWght = c(0.6236,
0.1251, 0.0929, 0.0627, 0.0483, 0.0455, 0.0674, 0.0488, 0.0376,
0.0286, 0.6462, 0.1708, 0.1169, 0.0672, 0.0448, 0.0639, 0.0655,
0.0482, 0.0376, 0.023), boleWght = c(5.6128, 1.1263, 0.8365,
0.5646, 0.4345, 0.2746, 0.134, 0.0291, 0.0148, 0.0077, 5.8161,
1.5374, 1.0519, 0.6045, 0.2776, 0.1766, 0.0823, 0.0281, 0.0149,
0.0045), deadFoliage = c(0.446, 0.446, 0.446, 0.446, 0.446,
0.446, 0.446, 0.446, 0.446, 0.446, 0.4278, 0.4278, 0.4278,
0.4278, 0.4278, 0.4278, 0.4278, 0.4278, 0.4278, 0.4278),
deadTwig = c(0.7874, 0.7874, 0.7874, 0.7874, 0.7874, 0.7874,
0.7874, 0.7874, 0.7874, 0.7874, 0.7322, 0.7322, 0.7322, 0.7322,
0.7322, 0.7322, 0.7322, 0.7322, 0.7322, 0.7322), deadbole = c(3.4762,
3.4762, 3.4762, 3.4762, 3.4762, 3.4762, 3.4762, 3.4762, 3.4762,
3.4762, 3.1449, 3.1449, 3.1449, 3.1449, 3.1449, 3.1449, 3.1449,
3.1449, 3.1449, 3.1449)), .Names = c("row", "col", "cell",
"xcoord", "ycoord", "species", "age", "biomass", "stems", "slowGrowth",
"DBH", "height", "availableLight", "light_rf", "LeafArea", "nitorgen_rf",
"droughtIndex", "moisture_rf", "degreeDay_rf", "foliageWght",
"twigWght", "boleWght", "deadFoliage", "deadTwig", "deadbole"
), row.names = c(NA, 20L), class = "data.frame")
Here is my code.
for (i in 0:1) {
t <- which(output100$cell == i)
a <-max(output100[c(t),8])
dom <- c(a, dom)
}
I want to get the maximum cell for the "t". Of course here it's just a small example (0:1), I have bigger dataset in real.

Answer 1

not sure what your problem is, your for loop runs for me. Did you forget to initialise dom?
dom = NULL
for (i in 0:1) {
t <- which(output100$cell == i)
a <-max(output100[c(t),8])
dom <- c(a, dom)
}
dom
## [1] 6.6135 6.3836
works for me? What answers are you expecting?
Incidentally this may not be the most efficient way to do this as you are growing the results vector in the for loop. If you had lots of unique cell values this would be slow. You could achieve similar by using dplyr which also would not require you to know how many different cell values there were:
library(dplyr)
output100 %>%
group_by(cell) %>%
summarise(max(biomass))
## # A tibble: 2 × 2
## cell `max(biomass)`
## <int> <dbl>
## 1 0 6.3836
## 2 1 6.6135