I'm aggregating data with variable bin sizes (see previous question here: R: aggregate every n rows with variable n depending on sum(n) of second column). In addition to calculating sums and means over groups of variable ranges, I need to pull out single-value covariates at the midpoint of each group range. When I try to do this on the fly, I only get a value for the first group and NAs for the remaining.
df.summary<-as.data.frame(df %>%
mutate(rn = row_number()) %>%
group_by(grp = (cumsum(d)-1)%/% 100 1) %>%
summarise(x=mean(x, na.rm = TRUE), d=sum(d, na.rm=T), ,i.start=first(rn), i.end=last(rn), y=nth(y, round(first(rn) (last(rn)-first(rn))/2-1))))
head(df.summary)
grp x d i.start i.end y
1 1 0.07458317 88.99342 1 4 19.78992
2 2 0.07594546 97.62130 5 8 NA
3 3 0.05353308 104.69683 9 12 NA
4 4 0.06498291 106.23468 13 16 NA
5 5 0.08601759 98.24939 17 20 NA
6 6 0.06262427 84.43745 21 23 NA
sample data:
structure(list(x = c(0.10000112377193, 0.110742170350877, 0.0300274304561404,
0.0575619395964912, 0.109060465438596, 0.0595491225614035, 0.0539270264912281,
0.0812452063859649, 0.0341699389122807, 0.0391744879122807, 0.0411787485614035,
0.0996091644385965, 0.0970479474912281, 0.0595715843684211, 0.0483489989122807,
0.0549631194561404, 0.0705080555964912, 0.080437472631579, 0.105883664631579,
0.0872411613684211, 0.103236660631579, 0.0381296894912281, 0.0465064491578947,
0.0936565184561403, 0.0410095752631579, 0.0311180032105263, 0.0257758157894737,
0.0354721928947368, 0.0584999394736842, 0.0241286060175439, 0.112053376666667,
0.0769823868596491, 0.0558137530526316, 0.0374491000701754, 0.0419279142631579,
0.0260257506842105, 0.0544360374561404, 0.107411071842105, 0.103873468,
0.0419322114035088, 0.0483912961052632, 0.0328373653157895, 0.0866868717719298,
0.063990467245614, 0.0799280314035088, 0.123490407070175, 0.145676836280702,
0.0292878782807018, 0.0432093036666667, 0.0203547443684211),
d = c(22.2483512600033, 22.2483529247042, 22.2483545865809,
22.2483562542823, 22.24835791863, 25.1243105415557, 25.1243148759953,
25.1243192107884, 25.1243235416981, 25.1243278750792, 27.2240858553058,
27.2240943134697, 27.2241027638674, 27.224111222031, 27.2241196741942,
24.5623431981188, 24.5623453409221, 24.5623474809012, 24.562349626705,
24.5623517696847, 28.1458125837154, 28.1458157376341, 28.1458188889053,
28.1458220452951, 28.1458251983314, 27.8293318542146, 27.8293366652115,
27.8293414829159, 27.829346292148, 27.8293511094993, 27.5271773325046,
27.5271834011289, 27.5271894694002, 27.5271955369655, 27.5272016048837,
28.0376097925214, 28.0376146410729, 28.0376194959786, 28.0376243427651,
28.0376291969647, 26.8766095768196, 26.8766122563318, 26.8766149309023,
26.8766176123562, 26.8766202925746, 27.8736950101666, 27.8736960528853,
27.8736971017815, 27.8736981446767, 27.8736991932199), y = c(19.79001,
19.789922, 19.789834, 19.789746, 19.789658, 19.78957, 19.789468,
19.789366, 19.789264, 19.789162, 19.78906, 19.78896, 19.78886,
19.78876, 19.78866, 19.78856, 19.788458, 19.788356, 19.788254,
19.788152, 19.78805, 19.787948, 19.787846, 19.787744, 19.787642,
19.78754, 19.787442, 19.787344, 19.787246, 19.787148, 19.78705,
19.786956, 19.786862, 19.786768, 19.786674, 19.78658, 19.786486,
19.786392, 19.786298, 19.786204, 19.78611, 19.786016, 19.785922,
19.785828, 19.785734, 19.78564, 19.785544, 19.785448, 19.785352,
19.785256)), row.names = c(NA, 50L), class = "data.frame")
CodePudding user response：
Let's add variable z and n in summarise part. Those variables are defined as below.
df %>%
mutate(rn = row_number()) %>%
group_by(grp = (cumsum(d)-1)%/% 100 1) %>%
summarise(x=mean(x, na.rm = TRUE),
d=sum(d, na.rm=T), ,i.start=first(rn),
i.end=last(rn),
z = round(first(rn) (last(rn)-first(rn))/2-1),
n = n())
grp x d i.start i.end z n
<dbl> <dbl> <dbl> <int> <int> <dbl> <int>
1 1 0.0746 89.0 1 4 2 4
2 2 0.0759 97.6 5 8 6 4
3 3 0.0535 105. 9 12 10 4
4 4 0.0650 106. 13 16 14 4
5 5 0.0860 98.2 17 20 18 4
6 6 0.0626 84.4 21 23 21 3
7 7 0.0479 112. 24 27 24 4
8 8 0.0394 83.5 28 30 28 3
9 9 0.0706 110. 31 34 32 4
10 10 0.0575 112. 35 38 36 4
11 11 0.0647 83.0 39 41 39 3
12 12 0.0659 108. 42 45 42 4
13 13 0.0854 111. 46 49 46 4
14 14 0.0204 27.9 50 50 49 1
In dataframe above, n indicates sample size of each groups separated by grp. However, as you state group_by(grp), when you call nth(y, z), YOU WILL CALL Z-TH VALUE BY GROUP.
It means that for 5th group, although there exists only 4 values, you call 18th value of y. So it prints NA.
To get this easy, the most simple way I think is use n().
df %>%
mutate(rn = row_number()) %>%
group_by(grp = (cumsum(d)-1)%/% 100 1) %>%
summarise(x=mean(x, na.rm = TRUE),
d=sum(d, na.rm=T), ,i.start=first(rn),
i.end=last(rn),
y=nth(y, round(n()/2)))
grp x d i.start i.end y
<dbl> <dbl> <dbl> <int> <int> <dbl>
1 1 0.0746 89.0 1 4 19.8
2 2 0.0759 97.6 5 8 19.8
3 3 0.0535 105. 9 12 19.8
4 4 0.0650 106. 13 16 19.8
5 5 0.0860 98.2 17 20 19.8
6 6 0.0626 84.4 21 23 19.8
7 7 0.0479 112. 24 27 19.8
8 8 0.0394 83.5 28 30 19.8
9 9 0.0706 110. 31 34 19.8
10 10 0.0575 112. 35 38 19.8
11 11 0.0647 83.0 39 41 19.8
12 12 0.0659 108. 42 45 19.8
13 13 0.0854 111. 46 49 19.8
14 14 0.0204 27.9 50 50 NA
You'll call floor(n/2)th y, which means y that locates middle of each group. Note that you can also try floor(n/2) 1.
CodePudding user response：
df %>%
mutate(rn = row_number()) %>%
group_by(grp = (cumsum(d)-1)%/% 100 1) %>%
summarise(x=mean(x, na.rm = TRUE),
d = sum(d, na.rm=T),
i.start=first(rn),
i.end=last(rn),
y = nth(y, floor(median(rn)) - i.start))