Efficient method for Iterating over rows and replace by get column method in a data table?
I am trying to iterate every rows and calculate Value from Columns A to E and corresponding column name from WhichCol. It works, but this step takes so long for 50,000 rows data. Is there an efficient way to do this?
library(data.table)
df<-structure(list(Id = 1:10, A = c(73L, 61L, 46L, 26L, 18L, 29L,
88L, 18L, 56L, 81L), B = c(68L, 49L, 27L, 10L, 37L, 72L, 71L,
60L, 52L, 62L), C = c(98L, 59L, 76L, 46L, 46L, 31L, 77L, 83L,
51L, 6L), D = c(40L, 18L, 27L, 18L, 72L, 95L, 87L, 29L, 35L,
80L), E = c(74L, 87L, 27L, 98L, 54L, 91L, 100L, 71L, 13L, 15L
), WhichCol = c("A", "C", "E", "B", "A", "D", "A", "C", "E",
"B"), Value = c(73L, 59L, 27L, 10L, 18L, 95L, 88L, 83L, 13L,
62L)), .Names = c("Id", "A", "B", "C", "D", "E", "WhichCol",
"Value"), class = "data.frame")
setDT(df)
df[["Value"]]<-sapply(1:nrow(df), function(x){ df[x, get(WhichCol)] })
Value column is added in the sample data here - but that's what I am trying to get..
r data.table
edited Nov 16 '18 at 7:58
LAP
5,7902723
asked Nov 16 '18 at 5:57
JeanVudaJeanVuda
1,011623
add a comment |
I am trying to iterate every rows and calculate Value from Columns A to E and corresponding column name from WhichCol. It works, but this step takes so long for 50,000 rows data. Is there an efficient way to do this?
library(data.table)
df<-structure(list(Id = 1:10, A = c(73L, 61L, 46L, 26L, 18L, 29L,
88L, 18L, 56L, 81L), B = c(68L, 49L, 27L, 10L, 37L, 72L, 71L,
60L, 52L, 62L), C = c(98L, 59L, 76L, 46L, 46L, 31L, 77L, 83L,
51L, 6L), D = c(40L, 18L, 27L, 18L, 72L, 95L, 87L, 29L, 35L,
80L), E = c(74L, 87L, 27L, 98L, 54L, 91L, 100L, 71L, 13L, 15L
), WhichCol = c("A", "C", "E", "B", "A", "D", "A", "C", "E",
"B"), Value = c(73L, 59L, 27L, 10L, 18L, 95L, 88L, 83L, 13L,
62L)), .Names = c("Id", "A", "B", "C", "D", "E", "WhichCol",
"Value"), class = "data.frame")
setDT(df)
df[["Value"]]<-sapply(1:nrow(df), function(x){ df[x, get(WhichCol)] })
Value column is added in the sample data here - but that's what I am trying to get..
r data.table
edited Nov 16 '18 at 7:58
LAP
5,7902723
asked Nov 16 '18 at 5:57
JeanVudaJeanVuda
1,011623
add a comment |
I am trying to iterate every rows and calculate Value from Columns A to E and corresponding column name from WhichCol. It works, but this step takes so long for 50,000 rows data. Is there an efficient way to do this?
library(data.table)
df<-structure(list(Id = 1:10, A = c(73L, 61L, 46L, 26L, 18L, 29L,
88L, 18L, 56L, 81L), B = c(68L, 49L, 27L, 10L, 37L, 72L, 71L,
60L, 52L, 62L), C = c(98L, 59L, 76L, 46L, 46L, 31L, 77L, 83L,
51L, 6L), D = c(40L, 18L, 27L, 18L, 72L, 95L, 87L, 29L, 35L,
80L), E = c(74L, 87L, 27L, 98L, 54L, 91L, 100L, 71L, 13L, 15L
), WhichCol = c("A", "C", "E", "B", "A", "D", "A", "C", "E",
"B"), Value = c(73L, 59L, 27L, 10L, 18L, 95L, 88L, 83L, 13L,
62L)), .Names = c("Id", "A", "B", "C", "D", "E", "WhichCol",
"Value"), class = "data.frame")
setDT(df)
df[["Value"]]<-sapply(1:nrow(df), function(x){ df[x, get(WhichCol)] })
Value column is added in the sample data here - but that's what I am trying to get..
r data.table
edited Nov 16 '18 at 7:58
LAP
5,7902723
asked Nov 16 '18 at 5:57
JeanVudaJeanVuda
1,011623
I am trying to iterate every rows and calculate Value from Columns A to E and corresponding column name from WhichCol. It works, but this step takes so long for 50,000 rows data. Is there an efficient way to do this?
library(data.table)
df<-structure(list(Id = 1:10, A = c(73L, 61L, 46L, 26L, 18L, 29L,
88L, 18L, 56L, 81L), B = c(68L, 49L, 27L, 10L, 37L, 72L, 71L,
60L, 52L, 62L), C = c(98L, 59L, 76L, 46L, 46L, 31L, 77L, 83L,
51L, 6L), D = c(40L, 18L, 27L, 18L, 72L, 95L, 87L, 29L, 35L,
80L), E = c(74L, 87L, 27L, 98L, 54L, 91L, 100L, 71L, 13L, 15L
), WhichCol = c("A", "C", "E", "B", "A", "D", "A", "C", "E",
"B"), Value = c(73L, 59L, 27L, 10L, 18L, 95L, 88L, 83L, 13L,
62L)), .Names = c("Id", "A", "B", "C", "D", "E", "WhichCol",
"Value"), class = "data.frame")
setDT(df)
df[["Value"]]<-sapply(1:nrow(df), function(x){ df[x, get(WhichCol)] })
Value column is added in the sample data here - but that's what I am trying to get..
r data.table
r data.table
edited Nov 16 '18 at 7:58
LAP
5,7902723
asked Nov 16 '18 at 5:57
JeanVudaJeanVuda
1,011623
edited Nov 16 '18 at 7:58
LAP
5,7902723
asked Nov 16 '18 at 5:57
JeanVudaJeanVuda
1,011623
edited Nov 16 '18 at 7:58
LAP
5,7902723
edited Nov 16 '18 at 7:58
LAP
5,7902723
edited Nov 16 '18 at 7:58
LAP
5,7902723
5,7902723
asked Nov 16 '18 at 5:57
JeanVudaJeanVuda
1,011623
asked Nov 16 '18 at 5:57
JeanVudaJeanVuda
1,011623
asked Nov 16 '18 at 5:57
JeanVudaJeanVuda
1,011623
1,011623
add a comment |
add a comment |
1 Answer
1
active
oldest
votes
You could instead of looping over each row, use the fact, that for each value of WhichCol you know which colum you want. (e.g. for every WhichCol == "A" take column A).
df[, ValueNew := get(unique(WhichCol)), by = WhichCol]
I did a little speed test:
n <- 1000
df <- rbindlist(rep(list(df), n))
# over unique WhichCol
system.time(df[, ValueNew := get(unique(WhichCol)), by = WhichCol])
user system elapsed
0.002 0.000 0.001
system.time(df[["Value2"]]<-sapply(1:nrow(df), function(x){ df[x, get(WhichCol)] }))
user system elapsed
5.445 0.021 5.472
I hope this will help you.
answered Nov 16 '18 at 16:22
Jakob GeppJakob Gepp
16818
add a comment |
Your Answer
StackExchange.ifUsing("editor", function () {
StackExchange.using("externalEditor", function () {
StackExchange.using("snippets", function () {
StackExchange.snippets.init();
});
});
}, "code-snippets");
StackExchange.ready(function() {
var channelOptions = {
tags: "".split(" "),
id: "1"
};
initTagRenderer("".split(" "), "".split(" "), channelOptions);
StackExchange.using("externalEditor", function() {
// Have to fire editor after snippets, if snippets enabled
if (StackExchange.settings.snippets.snippetsEnabled) {
StackExchange.using("snippets", function() {
createEditor();
});
}
else {
createEditor();
}
});
function createEditor() {
StackExchange.prepareEditor({
heartbeatType: 'answer',
autoActivateHeartbeat: false,
convertImagesToLinks: true,
noModals: true,
showLowRepImageUploadWarning: true,
reputationToPostImages: 10,
bindNavPrevention: true,
postfix: "",
imageUploader: {
brandingHtml: "Powered by u003ca class="icon-imgur-white" href="https://imgur.com/"u003eu003c/au003e",
contentPolicyHtml: "User contributions licensed under u003ca href="https://creativecommons.org/licenses/by-sa/3.0/"u003ecc by-sa 3.0 with attribution requiredu003c/au003e u003ca href="https://stackoverflow.com/legal/content-policy"u003e(content policy)u003c/au003e",
allowUrls: true
},
onDemand: true,
discardSelector: ".discard-answer"
,immediatelyShowMarkdownHelp:true
});
}
});
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
StackExchange.ready(
function () {
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fstackoverflow.com%2fquestions%2f53332221%2fefficient-method-for-iterating-over-rows-and-replace-by-get-column-method-in-a-d%23new-answer', 'question_page');
}
);
Post as a guest
Required, but never shown
1 Answer
1
active
oldest
votes
1 Answer
1
active
oldest
votes
active
oldest
votes
active
oldest
votes
You could instead of looping over each row, use the fact, that for each value of WhichCol you know which colum you want. (e.g. for every WhichCol == "A" take column A).
df[, ValueNew := get(unique(WhichCol)), by = WhichCol]
I did a little speed test:
n <- 1000
df <- rbindlist(rep(list(df), n))
# over unique WhichCol
system.time(df[, ValueNew := get(unique(WhichCol)), by = WhichCol])
user system elapsed
0.002 0.000 0.001
system.time(df[["Value2"]]<-sapply(1:nrow(df), function(x){ df[x, get(WhichCol)] }))
user system elapsed
5.445 0.021 5.472
I hope this will help you.
answered Nov 16 '18 at 16:22
Jakob GeppJakob Gepp
16818
add a comment |
You could instead of looping over each row, use the fact, that for each value of WhichCol you know which colum you want. (e.g. for every WhichCol == "A" take column A).
df[, ValueNew := get(unique(WhichCol)), by = WhichCol]
I did a little speed test:
n <- 1000
df <- rbindlist(rep(list(df), n))
# over unique WhichCol
system.time(df[, ValueNew := get(unique(WhichCol)), by = WhichCol])
user system elapsed
0.002 0.000 0.001
system.time(df[["Value2"]]<-sapply(1:nrow(df), function(x){ df[x, get(WhichCol)] }))
user system elapsed
5.445 0.021 5.472
I hope this will help you.
answered Nov 16 '18 at 16:22
Jakob GeppJakob Gepp
16818
add a comment |
You could instead of looping over each row, use the fact, that for each value of WhichCol you know which colum you want. (e.g. for every WhichCol == "A" take column A).
df[, ValueNew := get(unique(WhichCol)), by = WhichCol]
I did a little speed test:
n <- 1000
df <- rbindlist(rep(list(df), n))
# over unique WhichCol
system.time(df[, ValueNew := get(unique(WhichCol)), by = WhichCol])
user system elapsed
0.002 0.000 0.001
system.time(df[["Value2"]]<-sapply(1:nrow(df), function(x){ df[x, get(WhichCol)] }))
user system elapsed
5.445 0.021 5.472
I hope this will help you.
answered Nov 16 '18 at 16:22
Jakob GeppJakob Gepp
16818
You could instead of looping over each row, use the fact, that for each value of WhichCol you know which colum you want. (e.g. for every WhichCol == "A" take column A).
df[, ValueNew := get(unique(WhichCol)), by = WhichCol]
I did a little speed test:
n <- 1000
df <- rbindlist(rep(list(df), n))
# over unique WhichCol
system.time(df[, ValueNew := get(unique(WhichCol)), by = WhichCol])
user system elapsed
0.002 0.000 0.001
system.time(df[["Value2"]]<-sapply(1:nrow(df), function(x){ df[x, get(WhichCol)] }))
user system elapsed
5.445 0.021 5.472
I hope this will help you.
answered Nov 16 '18 at 16:22
Jakob GeppJakob Gepp
16818
answered Nov 16 '18 at 16:22
Jakob GeppJakob Gepp
16818
answered Nov 16 '18 at 16:22
Jakob GeppJakob Gepp
16818
answered Nov 16 '18 at 16:22
Jakob GeppJakob Gepp
16818
16818
add a comment |
add a comment |
Thanks for contributing an answer to Stack Overflow!
- Please be sure to answer the question. Provide details and share your research!
But avoid …
- Asking for help, clarification, or responding to other answers.
- Making statements based on opinion; back them up with references or personal experience.
To learn more, see our tips on writing great answers.
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
StackExchange.ready(
function () {
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fstackoverflow.com%2fquestions%2f53332221%2fefficient-method-for-iterating-over-rows-and-replace-by-get-column-method-in-a-d%23new-answer', 'question_page');
}
);
Post as a guest
Required, but never shown
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
