Deriving contingency table from a bigger contingency table in R - r

I have a csv format contingency table made by python language , like this:
case control
disease_A 20 30
disease_B 35 45
disease_C 42 52
disease_D 52 62
now i want to derive 2x2 contingency tables from this contingency table to calculate chi-square value using R
how can i derive a 2x2 table like the following from the contingency table above:
case control
disease_A 20 30
disease_D 52 62
Thats probably a novice question but im new to R and i couldn't find the solution anywhere else

Here's an approach.
The data:
txt <- " case control
disease_A 20 30
disease_B 35 45
disease_C 42 52
disease_D 52 62"
Read the data:
dat <- read.table(textConnection(txt))
# case control
# disease_A 20 30
# disease_B 35 45
# disease_C 42 52
# disease_D 52 62
Extract a subset of rows:
dat2 <- dat[rownames(dat) %in% c("disease_A", "disease_D"), ]
# case control
# disease_A 20 30
# disease_D 52 62

If M is of class table
M <- structure(c(20, 35, 42, 52, 30, 45, 52, 62), .Dim = c(4L, 2L), .Dimnames = list(
c("disease_A", "disease_B", "disease_C", "disease_D"), c("case",
"control")), class = "table")
xtabs(Freq~Var1+Var2,data= subset(as.data.frame(M,stringsAsFactors=F),
Var1%in% c("disease_A", "disease_D")))
Var2
Var1 case control
disease_A 20 30
disease_D 52 62
If M is a data.frame
M <- structure(list(case = c(20L, 35L, 42L, 52L), control = c(30L,
45L, 52L, 62L)), .Names = c("case", "control"), class = "data.frame", row.names = c("disease_A",
"disease_B", "disease_C", "disease_D"))
as.table(as.matrix(M[grep("A|D", rownames(M)),]))

Related

Calculating Percent Change in R for Multiple Variables

I'm trying to calculate percent change in R with each of the time points included in the column label (table below). I have dplyr loaded and my dataset was loaded in R and I named it data. Below is the code I'm using but it's not calculating correctly. I want to create a new dataframe called data_per_chg which contains the percent change from "v1" each variable from. For instance, for wbc variable, I would like to calculate percent change of wbc.v1 from wbc.v1, wbc.v2 from wbc.v1, wbc.v3 from wbc.v1, etc, and do that for all the remaining variables in my dataset. I'm assuming I can probably use a loop to easily do this but I'm pretty new to R so I'm not quite sure how proceed. Any guidance will be greatly appreciated.
id
wbc.v1
wbc.v2
wbc.v3
rbc.v1
rbc.v2
rbc.v3
hct.v1
hct.v2
hct.v3
a1
23
63
30
23
56
90
13
89
47
a2
81
45
46
N/A
18
78
14
45
22
a3
NA
27
14
29
67
46
37
34
33
data_per_chg<-data%>%
group_by(id%>%
arrange(id)%>%
mutate(change=(wbc.v2-wbc.v1)/(wbc.v1))
data_per_chg
Assuming the NA values are all NA and no N/A
library(dplyr)
library(stringr)
data <- data %>%
na_if("N/A") %>%
type.convert(as.is = TRUE) %>%
mutate(across(-c(id, matches("\\.v1$")), ~ {
v1 <- get(str_replace(cur_column(), "v\\d+$", "v1"))
(.x - v1)/v1}, .names = "{.col}_change"))
-output
data
id wbc.v1 wbc.v2 wbc.v3 rbc.v1 rbc.v2 rbc.v3 hct.v1 hct.v2 hct.v3 wbc.v2_change wbc.v3_change rbc.v2_change rbc.v3_change hct.v2_change hct.v3_change
1 a1 23 63 30 23 56 90 13 89 47 1.7391304 0.3043478 1.434783 2.9130435 5.84615385 2.6153846
2 a2 81 45 46 NA 18 78 14 45 22 -0.4444444 -0.4320988 NA NA 2.21428571 0.5714286
3 a3 NA 27 14 29 67 46 37 34 33 NA NA 1.310345 0.5862069 -0.08108108 -0.1081081
If we want to keep the 'v1' columns as well
data %>%
na_if("N/A") %>%
type.convert(as.is = TRUE) %>%
mutate(across(ends_with('.v1'), ~ .x - .x,
.names = "{str_replace(.col, 'v1', 'v1change')}")) %>%
transmute(id, across(ends_with('change')),
across(-c(id, matches("\\.v1$"), ends_with('change')),
~ {
v1 <- get(str_replace(cur_column(), "v\\d+$", "v1"))
(.x - v1)/v1}, .names = "{.col}_change")) %>%
select(id, starts_with('wbc'), starts_with('rbc'), starts_with('hct'))
-output
id wbc.v1change wbc.v2_change wbc.v3_change rbc.v1change rbc.v2_change rbc.v3_change hct.v1change hct.v2_change hct.v3_change
1 a1 0 1.7391304 0.3043478 0 1.434783 2.9130435 0 5.84615385 2.6153846
2 a2 0 -0.4444444 -0.4320988 NA NA NA 0 2.21428571 0.5714286
3 a3 NA NA NA 0 1.310345 0.5862069 0 -0.08108108 -0.1081081
data
data <- structure(list(id = c("a1", "a2", "a3"), wbc.v1 = c(23L, 81L,
NA), wbc.v2 = c(63L, 45L, 27L), wbc.v3 = c(30L, 46L, 14L), rbc.v1 = c("23",
"N/A", "29"), rbc.v2 = c(56L, 18L, 67L), rbc.v3 = c(90L, 78L,
46L), hct.v1 = c(13L, 14L, 37L), hct.v2 = c(89L, 45L, 34L), hct.v3 = c(47L,
22L, 33L)), class = "data.frame", row.names = c(NA, -3L))

How to join and bind similar dataframes in R, iterative solutions welcome

In R markdown through R Studio (R v. 4.0.3), I'm looking for a better solution to combining similarly structured dataframes while keeping all rows and matching entries on a key. Piping full_join() into a filter into a bind_rows() directly wasn't working, possibly because of the error message:
Error: Can't combine ..1$term_code 'character> and ..2$term_code '<integer.
I have 23 dataframes (let's call these "semester data") of data I'm looking to combine into a single dataframe (intended to be a single dataset of individuals outcomes from semester-to-semester).
Each semester dataframe is roughly 3000-4000 observations (individuals) with 45-47 variables of relevant data. A simplified example of a semester (or term) dataframe is shown below.
Simplified example of a "semester" dataframe:
id
ACT_math
course_code
section_code
term_code
grade
term_GPA
0001
23
101
001
FA12
3.45
3.8
0002
28
201
003
FA12
3.2
3.4
Individuals will show up in multiple semester dataframes as they progress through the program (taking course 101 in the fall and course 102 in the spring).
I want to use the dplyr full_join() to match these individuals on an ID key.
Using the suffix argument, I hope to keep track of which semester and course a set of data (grade, term_GPA, etc) for an individual comes from.
There's some data (ACT score, gender, state residency, etc) that is the stable for an individual across semester dataframes. Ideally I could take the first input and drop the rest, but if I had to clean this afterwards, that's fine.
I started by defining an object programatic_database using the first semester of data SP11. To cut down on the duplication of stable data for an individual, I selected the relevant columns that I wanted to join.
programmatic_database <- programmatic_database %>%
full_join(select(fa12, id, course_code, section_code, grade, term_gpa), by = "id", copy = TRUE, suffix = c(".sp11", ".fa12"), keep = FALSE, name = "id")
However, every semester new students join the program. I would like to add these entries to the bottom of the growing programmatic_database.
I'm also looking to use rbind() or bind_rows() to add these individuals to the bottom of the programmatic_database, along with their relevant data.
After full_join(), I'm filtering out the entries that have already been added horizontally to the dataframe, then piping the remaining entries into bind_rows()
programmatic_database <- fa12[!which(fa12$id %in% programmatic_database),] %>% dplyr::bind_rows(programmatic_database, fa12)
Concatenated example of what my code is producing after several iterations:
id
ACT_math
course_code
section_code
section_code.db
section_code.db.db
term_code
grade.sp11
grade.fa12
grade.sp13
grade.sp15
term_GPA.sp11
term_GPA.fa12
term_GPA.sp15
0001
23
102
001
001
001
FA12
3.45
3.8
3.0
-
3.8
3.7
-
0002
28
201
003
003
003
FA12
3.2
3.4
3.0
-
3.8
3.7
-
1020
28
201
003
003
003
FA12
3.2
3.4
-
-
3.8
3.7
-
6783
30
101
-
-
-
SP15
-
-
-
3.8
-
-
4.0
where I have successfully added horizontally for students 0001 and 0002 for outcomes in subsequent courses in subsequent semesters. I have also managed to add vertically, like with student 6783, leaving blanks for previous semesters before they enrolled but still adding the relevant columns.
Questions:
Is there a way to pipe full_join() into a filter() into a bind_rows() without running into these errors?
rbind number of columns do not match
OR
Error: Can't combine ..1$term_code 'character> and ..2$term_code '<integer.
Is there a easy way to keep certain columns and only add the suffix ".fa12" to certain columns? As you can see, the .db is piling up.
Is there any way to automate this? Loops aren't my strong suit, but I'm sure there's a better-looking code than doing each of the 23 joins/binds by hand.
Thank you for assistance!
Current code for simplicity:
#reproducible example
fa11 <- structure(list(id = c("1001", "1002", "1003",
"1013"), act6_05_composite = c(33L, 26L, 27L, 25L), course_code = c("101",
"101", "101", "101"), term_code = c("FA11", "FA11", "FA11", "FA11"
), section_code = c(1L, 1L, 1L, 1L), grade = c(4, 0, 0, 2.5
), repeat_status_flag = c(NA, "PR", NA, NA), class_code = c(1L,
1L, 1L, 1L), cum_atmpt_credits_prior = c(16, 0, 0, 0), cum_completed_credits_prior = c(0L,
0L, 0L, 0L), cum_passed_credits_prior = c(16, 0, 0, 0), cum_gpa_prior = c(0,
0, 0, 0), cum_atmpt_credits_during = c(29, 15, 18, 15), cum_completed_credits_during = c(13L,
1L, 10L, 15L), cum_passed_credits_during = c(29, 1, 14, 15),
term_gpa = c(3.9615, 0.2333, 2.3214, 2.9666), row.names = c(NA, 4L
), class = "data.frame")
sp12 <- structure(list(id = c("1007", "1013", "1355",
"2779", "2302"), act6_05_composite = c(24L, 26L, 25L, 24L,
24L), course_code = c(101L, 102L, 101L, 101L, 101L
), term_code = c(NA_integer_, NA_integer_, NA_integer_, NA_integer_,
NA_integer_), section_code = c(1L, 1L, 1L, 1L, 1L), grade = c(2,
2.5, 2, 1.5, 3.5), repeat_status_flag = c(NA_character_,
NA_character_, NA_character_, NA_character_, NA_character_
), class_code = c(2L, 2L, 1L, 2L, 2L), cum_atmpt_credits_prior = c(44,
43, 12, 43, 30), cum_completed_credits_prior = c(41L, 43L,
12L, 43L, 12L), cum_passed_credits_prior = c(41, 43, 12,
43, 30), cum_gpa_prior = c(3.3125, 3.186, 3.5416, 3.1785,
3.8636), cum_atmpt_credits_during = c(56, 59, 25, 64, 43),
cum_completed_credits_during = c(53L, 56L, 25L, 56L, 25L),
cum_passed_credits_during = c(53, 59, 25, 64, 43), term_gpa = c(2.8333,
3.423, 3.1153, 2.1923, 3.6153), row.names = c(NA,
5L), class = "data.frame")
# make object from fall 2011 semester dataframe
programmatic_database <- fa11
# join the spring 2012 semester dataframe by id using select variables and attaching relevant suffix
programmatic_database <- programmatic_database %>%
full_join(select(sp12, id, course_code, section_code, grade, term_gpa), by = "id", copy = TRUE, suffix = c(".fa11", ".sp12"), keep = FALSE, name = "id")
#view results of join, force integer type on certain variables as needed (see error above)
#filter the joined entries from fall 2012 database, then bind the remaining entries to the bottom of the growing dataset
programmatic_database <- sp12[!which(sp12$id %in% programmatic_database),] %>% dplyr::bind_rows(programmatic_database, sp12)
It would be possible to use bind_rows here if you make the column types consistent between tables. For instance, you could make a function to re-type any particular columns that aren't consistent in your original data. (That might also be something you could fix upstream as you read it in.)
library(dplyr)
set_column_types <- function(df) {
df %>%
mutate(term_code = as.character(term_code),
course_code = as.character(course_code))
}
bind_rows(
fa11 %>% set_column_types(),
sp12 %>% set_column_types() %>% mutate(term_code = "SP12")
)
This will stack your data into a relatively "long" format, like below. You may want to then reshape it depending on what kind of subsequent calculations you want to do.
id act6_05_composite course_code term_code section_code grade repeat_status_flag class_code cum_atmpt_credits_prior cum_completed_credits_prior cum_passed_credits_prior cum_gpa_prior cum_atmpt_credits_during cum_completed_credits_during cum_passed_credits_during term_gpa
1 1001 33 101 FA11 1 4.0 <NA> 1 16 0 16 0.0000 29 13 29 3.9615
2 1002 26 101 FA11 1 0.0 PR 1 0 0 0 0.0000 15 1 1 0.2333
3 1003 27 101 FA11 1 0.0 <NA> 1 0 0 0 0.0000 18 10 14 2.3214
4 1013 25 101 FA11 1 2.5 <NA> 1 0 0 0 0.0000 15 15 15 2.9666
5 1007 24 101 SP12 1 2.0 <NA> 2 44 41 41 3.3125 56 53 53 2.8333
6 1013 26 102 SP12 1 2.5 <NA> 2 43 43 43 3.1860 59 56 59 3.4230
7 1355 25 101 SP12 1 2.0 <NA> 1 12 12 12 3.5416 25 25 25 3.1153
8 2779 24 101 SP12 1 1.5 <NA> 2 43 43 43 3.1785 64 56 64 2.1923
9 2302 24 101 SP12 1 3.5 <NA> 2 30 12 30 3.8636 43 25 43 3.6153

Correlation of similar variables in R

I have slightly edited the data table.
I would like to correlate variable with similar name in my dataset:
A_y B_y C_y A_p B_p C_p
1 15 52 32 30 98 56
2 30 99 60 56 46 25
3 10 25 31 20 22 30
..........
n 55 23 85 12 34 52
I would like to obtain correlation of
A_y-A_p: 0.78
B_y-B_p: 0.88
C_y-C_p: 0.93
How can I do it in R? Is it possible?
This is really dangerous. Behavior of data.frames with invalid column names is undefined by the language definition. Duplicated column names are invalid.
You should restructure your input data. Anyway, here is an approach with your input data.
DF <- read.table(text = " A B C A B C
1 15 52 32 30 98 56
2 30 99 60 56 46 25
3 10 25 31 20 22 30", header = TRUE, check.names = FALSE)
sapply(unique(names(DF)), function(s) do.call(cor, unname(DF[, names(DF) == s])))
# A B C
#0.9995544 0.1585501 -0.6004010
#compare:
cor(c(15, 30, 10), c(30, 56, 20))
#[1] 0.9995544
Here is another base R option
within(
rev(
stack(
Map(
function(x) do.call(cor, unname(x)),
split.default(df, unique(gsub("_.*", "", names(df))))
)
)
),
ind <- sapply(
ind,
function(x) {
paste0(grep(paste0("^", x), names(df), value = TRUE),
collapse = "-"
)
}
)
)
which gives
ind values
1 A_y-A_p 0.9995544
2 B_y-B_p 0.1585501
3 C_y-C_p -0.6004010
Data
df <- structure(list(A_y = c(15L, 30L, 10L), B_y = c(52L, 99L, 25L),
C_y = c(32L, 60L, 31L), A_p = c(30L, 56L, 20L), B_p = c(98L,
46L, 22L), C_p = c(56L, 25L, 30L)), class = "data.frame", row.names = c("1",
"2", "3"))

Subset data frame with matrix of logical values

Problem
I have data on two measures for four individuals each in a wide format. The measures are x and y and the individuals are A, B, C, D. The data frame looks like this
d <- data.frame(matrix(sample(1:100, 40, replace = F), ncol = 8))
colnames(d) <- paste(rep(c("x.", "y."),each = 4), rep(LETTERS[1:4], 2), sep ="")
d
x.A x.B x.C x.D y.A y.B y.C y.D
1 56 65 42 96 100 76 39 26
2 19 93 94 75 63 78 5 44
3 22 57 15 62 2 29 89 79
4 49 13 95 97 85 81 60 37
5 45 38 24 91 23 82 83 72
Now, would I would like to obtain for each row is the value of y for the individual with the lowest value of x.
So in the example above, the lowest value of x in row 1 is for individual C. Hence, for row 1 I would like to obtain y.C which is 39.
In the example, the resulting vector should be 39, 63, 89, 81, 83.
Approach
I have tried to get to this by first generating a matrix of the subset of d for the values of x.
t(apply(d[,1:4], 1, function(x) min(x) == x))
x.A x.B x.C x.D
[1,] FALSE FALSE TRUE FALSE
[2,] TRUE FALSE FALSE FALSE
[3,] FALSE FALSE TRUE FALSE
[4,] FALSE TRUE FALSE FALSE
[5,] FALSE FALSE TRUE FALSE
Now I wanted to apply this matrix to subset the subset of the data frame for the values of y. But I cannot find a way to achieve this.
Any help is much appreciated. Suggestions for a totally different - more elegant - approach are highly welcome too.
Thanks a lot!
We subset the dataset with the columns starting with 'x' ('dx') and 'y' ('dy'). Get the column index of the minimum value in each row of 'dx' using max.col, cbind with the row index and get the corresponding elements in 'dy'.
dx <- d[grep('^x', names(d))]
dy <- d[grep('^y', names(d))]
dy[cbind(1:nrow(dx),max.col(-dx, 'first'))]
#[1] 39 63 89 81 83
The above can be easily be converted to a function
get_min <- function(dat){
dx <- dat[grep('^x', names(dat))]
dy <- dat[grep('^y', names(dat))]
dy[cbind(1:nrow(dx), max.col(-dx, 'first'))]
}
get_min(d)
#[1] 39 63 89 81 83
Or using the OP's apply based method
t(d[,5:8])[apply(d[,1:4], 1, function(x) min(x) == x)]
#[1] 39 63 89 81 83
data
d <- structure(list(x.A = c(56L, 19L, 22L, 49L, 45L),
x.B = c(65L,
93L, 57L, 13L, 38L), x.C = c(42L, 94L, 15L, 95L, 24L),
x.D = c(96L,
75L, 62L, 97L, 91L), y.A = c(100L, 63L, 2L, 85L, 23L),
y.B = c(76L,
78L, 29L, 81L, 82L), y.C = c(39L, 5L, 89L, 60L, 83L),
y.D = c(26L,
44L, 79L, 37L, 72L)), .Names = c("x.A", "x.B", "x.C",
"x.D",
"y.A", "y.B", "y.C", "y.D"), class = "data.frame",
row.names = c("1", "2", "3", "4", "5"))
Here is my solution. The core idea is that there are functions which.min, which.max that can be row applied to the data frame:
Edit:
Now, would I would like to obtain for each row is the value of y for
the individual with the lowest value of x.
ind <- apply(d[ ,1:4], 1, which.min) # build column index by row
res <- d[,5:8][cbind(1:nrow(d), ind)] # rows are in order, select values by matrix
names(res) <- colnames(d)[5:8][ind] # set colnames as names from the sample column
res
y.D y.B y.D y.A y.D
18 46 16 85 80
Caveat: only works if individuals are in the same order for treatment x. and y. and all individuals present. Otherwise you can use grep like in Akrun's solution.
# My d was:
x.A x.B x.C x.D y.A y.B y.C y.D
1 88 96 65 55 14 99 63 18
2 12 11 27 45 70 46 20 69
3 32 81 21 9 77 44 91 16
4 8 84 42 78 85 94 28 90
5 31 51 83 2 67 25 54 80
We can create a function as follows,
get_min <- function(x){
d1 <- x[,1:4]
d2 <- x[,5:8]
mtrx <- as.matrix(d2[,apply(d1, 1, which.min)])
a <- row(mtrx) - col(mtrx)
split(mtrx, a)$"0"
}
get_min(d)
#[1] 39 63 89 81 83

Matching dataframes with data.table

I need to fill a matrix (MA) with information from a long data frame (DF) using another matrix as identifier (ID.MA).
An idea of my three matrices:
MA.ID creates an identifier to look in the big DF the needed variables:
a b c
a ID.aa ID.ab ID.ac
b ID.ba ID.bb ID.bc
c ID.ca ID.cb ID.cc
The original big data frame has useless information but has also the rows that are useful for me to fill the target MA matrix:
ID 1990 1991 1992
ID.aa 10 11 12
ID.ab 13 14 15
ID.ac 16 17 18
ID.ba 19 20 21
ID.bb 22 23 24
ID.bc 25 26 27
ID.ca 28 29 30
ID.cb 31 32 33
ID.cc 34 35 36
ID.xx 40 40 55
ID.xy 50 51 45
....
MA should be filled with cross-information. In my example it should look like that for a chosen column of DF (let's say, 1990):
a b c
a 10 13 16
b 19 22 25
c 28 31 34
I've tried to use match but honestly it didn't work out:
MA$a = DF[match(MA.ID$a, DF$ID),2]
I was recommended to use the data.table package but I couldn't see how that would help me.
Anyone has any good way to approach this problem?
Supposing that your input are dataframes, then you could do the following:
library(data.table)
setDT(ma)[, lapply(.SD, function(x) x = unlist(df[match(x,df$ID), "1990"]))
, .SDcols = colnames(ma)]
which returns:
a b c
1: 10 13 16
2: 19 22 25
3: 28 31 34
Explanation:
With setDT(ma) you transform the dataframe into a datatable (which is an enhanced dataframe).
With .SDcols=colnames(ma) you specify on which columns the transformation has to be applied.
lapply(.SD, function(x) x = unlist(df[match(x,df$ID),"1990"])) performs the matching operation on each column specified with .SDcols.
An alternative approach with data.table is first transforming ma to a long data.table:
ma2 <- melt(setDT(ma), measure.vars = c("a","b","c"))
setkey(ma2, value) # set key by which 'ma' has to be indexed
setDT(df, key="ID") # transform to a datatable & set key by which 'df' has to be indexed
# joining the values of the 1990 column of df into
# the right place in the value column of 'ma'
ma2[df, value := `1990`]
which gives:
> ma2
variable value
1: a 10
2: b 13
3: c 16
4: a 19
5: b 22
6: c 25
7: a 28
8: b 31
9: c 34
The only drawback of this method is that the numeric values in the 'value' column get stored as character values. You can correct this by extending it as follows:
ma2[df, value := `1990`][, value := as.numeric(value)]
If you want to change it back to wide format you could use the rowid function within dcast:
ma3 <- dcast(ma2, rowid(variable) ~ variable, value.var = "value")[, variable := NULL]
which gives:
> ma3
a b c
1: 10 13 16
2: 19 22 25
3: 28 31 34
Used data:
ma <- structure(list(a = structure(1:3, .Label = c("ID.aa", "ID.ba", "ID.ca"), class = "factor"),
b = structure(1:3, .Label = c("ID.ab", "ID.bb", "ID.cb"), class = "factor"),
c = structure(1:3, .Label = c("ID.ac", "ID.bc", "ID.cc"), class = "factor")),
.Names = c("a", "b", "c"), class = "data.frame", row.names = c(NA, -3L))
df <- structure(list(ID = structure(1:9, .Label = c("ID.aa", "ID.ab", "ID.ac", "ID.ba", "ID.bb", "ID.bc", "ID.ca", "ID.cb", "ID.cc"), class = "factor"),
`1990` = c(10L, 13L, 16L, 19L, 22L, 25L, 28L, 31L, 34L),
`1991` = c(11L, 14L, 17L, 20L, 23L, 26L, 29L, 32L, 35L),
`1992` = c(12L, 15L, 18L, 21L, 24L, 27L, 30L, 33L, 36L)),
.Names = c("ID", "1990", "1991", "1992"), class = "data.frame", row.names = c(NA, -9L))
In base R, it can be seen as a job for outer:
> outer(1:nrow(MA.ID), 1:ncol(MA.ID), Vectorize(function(x,y) {DF[which(DF$ID==MA.ID[x,y]),'1990']}))
[,1] [,2] [,3]
[1,] 10 13 16
[2,] 19 22 25
[3,] 28 31 34
Explanations:
outer creates a matrix as the outer product of the first argument X (here a b c) and the second argument Y (here the same, a b c)
for every combination of X and Y, it applies a function that looks up the value in DF, at the row where the ID is MA.ID[X,Y], and at the column 1990
the important trick here is to wrap the function with Vectorize, because outer expects a vectorized function
the result is finally returned as matrix
Alternatively, another way to do it (still in base R) is:
to convert your data frame MA.ID into a vector
sapply a quick function that looks up correspondance with DF$ID
and convert back to a matrix.
This works:
> structure(
sapply(unlist(MA.ID),
function(id){DF[which(DF$ID==id),'1990']}),
dim=dim(MA.ID), names=NULL)
[,1] [,2] [,3]
[1,] 10 13 16
[2,] 19 22 25
[3,] 28 31 34
(here the call to structure(..., dim=dim(MA.ID), names=NULL) converts back the vector to a matrix)

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