I am trying to use dplyr's new NSE language approach to create a conditional mutate, using a vector input. Where I am having trouble is setting the column equal to itself, see mwe below:
df <- data.frame("Name" = c(rep("A", 3), rep("B", 3), rep("C", 4)),
"X" = runif(1:10),
"Y" = runif(1:10)) %>%
tbl_df() %>%
mutate_if(is.factor, as.character)
ColToChange <- "Name"
ToChangeTo <- "Big"
Now, using the following:
df %>% mutate( !!ColToChange := ifelse(X >= 0.5 & Y >= 0.5, ToChangeTo, !!ColToChange))
Sets the ColToChange value to Name, not back to its original value. I am thus trying to use the syntax above to achieve this:
df %>% mutate( !!ColToChange := ifelse(X >= 0.5 & Y >= 0.5, ToChangeTo, Name))
But instead of Name, have it be the vector.
You need to use rlang:sym to evaluate ColToChange as a symbol Name first, then evaluate it as a column with !!:
library(rlang); library(dplyr);
df %>% mutate(!!ColToChange := ifelse(X >= 0.5 & Y >= 0.5, ToChangeTo, !!sym(ColToChange)))
# A tibble: 10 x 3
# Name X Y
# <chr> <dbl> <dbl>
# 1 A 0.05593119 0.3586310
# 2 A 0.70024660 0.4258297
# 3 Big 0.95444388 0.7152358
# 4 B 0.45809482 0.5256475
# 5 Big 0.71348123 0.5114379
# 6 B 0.80382633 0.2665391
# 7 Big 0.99618062 0.5788778
# 8 Big 0.76520307 0.6558515
# 9 C 0.63928001 0.1972674
#10 C 0.29963517 0.5855646
Related
Say I have a data frame:
df <- data.frame(a = 1:10,
b = 1:10,
c = 1:10)
I'd like to apply several summary functions to each column, so I use dplyr::summarise_all
library(dplyr)
df %>% summarise_all(.funs = c(mean, sum))
# a_fn1 b_fn1 c_fn1 a_fn2 b_fn2 c_fn2
# 1 5.5 5.5 5.5 55 55 55
This works great! Now, say I have a function that takes an extra parameter. For example, this function calculates the number of elements in a column above a threshold. (Note: this is a toy example and not the real function.)
n_above_threshold <- function(x, threshold) sum(x > threshold)
So, the function works like this:
n_above_threshold(1:10, 5)
#[1] 5
I can apply it to all columns like before, but this time passing the additional parameter, like so:
df %>% summarise_all(.funs = c(mean, n_above_threshold), threshold = 5)
# a_fn1 b_fn1 c_fn1 a_fn2 b_fn2 c_fn2
# 1 5.5 5.5 5.5 5 5 5
But, say I have a vector of thresholds where each element corresponds to a column. Say, c(1, 5, 7) for my example above. Of course, I can't simply do this, as it doesn't make any sense:
df %>% summarise_all(.funs = c(mean, n_above_threshold), threshold = c(1, 5, 7))
If I was using base R, I might do this:
> mapply(n_above_threshold, df, c(1, 5, 7))
# a b c
# 9 5 3
Is there a way of getting this result as part of a dplyr piped workflow like I was using for the simpler cases?
dplyr provides a bunch of context-dependent functions. One is cur_column(). You can use it in summarise to look up the threshold for a given column.
library("tidyverse")
df <- data.frame(
a = 1:10,
b = 1:10,
c = 1:10
)
n_above_threshold <- function(x, threshold) sum(x > threshold)
# Pair the parameters with the columns
thresholds <- c(1, 5, 7)
names(thresholds) <- colnames(df)
df %>%
summarise(
across(
everything(),
# Use `cur_column()` to access each column name in turn
list(count = ~ n_above_threshold(.x, thresholds[cur_column()]),
mean = mean)
)
)
#> a_count a_mean b_count b_mean c_count c_mean
#> 1 9 5.5 5 5.5 3 5.5
This returns NA silently if the current column name doesn't have a known threshold. This is something that you might or might not want to happen.
df %>%
# Add extra column to show what happens if we don't know the threshold for a column
mutate(
x = 1:10
) %>%
summarise(
across(
everything(),
# Use `cur_column()` to access each column name in turn
list(count = ~ n_above_threshold(.x, thresholds[cur_column()]),
mean = mean)
)
)
#> a_count a_mean b_count b_mean c_count c_mean x_count x_mean
#> 1 9 5.5 5 5.5 3 5.5 NA 5.5
Created on 2022-03-11 by the reprex package (v2.0.1)
I have this type of data:
df <- data.frame(
Utt = c(rep("oh", 10), rep("ah", 10)),
name = rep(LETTERS[1:2], 10),
value = c(0.5,2,2,2,2,1,0,1,3.5,1,
2.2,2.3,1.9,0.1,0.3,1.8,3,4,3.5,2)
)
I need to know whether within in each group of Utt and name, there are continuous value increases and how large these increases are.
EDIT: I've cobbled together this code, which produces the right result but seems convoluted:
df %>%
# order by name:
arrange(name) %>%
group_by(name, Utt) %>%
# mutate:
mutate(
# is there an increase from one value to the next?
is_increase = ifelse(lag(value) < value, value, NA),
# what's the difference between these values?
diff = is_increase - lag(value)) %>%
group_by(name, Utt, grp = rleid(!is.na(diff))) %>%
# sum the contiguous values:
summarise(increase_size = sum(diff, na.rm = TRUE)) %>%
# remove 0 values:
filter(!increase_size == 0) %>%
# put same-group increase_sizes in the same row:
summarise(
increase_size = str_c(increase_size, collapse = ', '))
# A tibble: 3 x 3
# Groups: name [2]
name Utt increase_size
<chr> <chr> <chr>
1 A ah 3.2
2 A oh 1.5, 3.5
3 B ah 3.9
NOTE: Ideally, the expected outcome would be:
1 A ah 3.2
2 A oh 1.5, 3.5
3 B ah 3.9
4 B oh NA
Is there a better (i.e., more concise, more clever) dplyr solution?
Use this function to find what you want.
f <- function(x) {
ind <- which(x > lag(x))
if (length(ind) == 0) {
return(NA)
}
ind2 <- ind[which(lead(ind, default = max(ind) + 2) - ind > 1)]
ind1 <- ind[which(ind - lag(ind, default = min(ind) - 2) > 1)] - 1
return(paste0(x[ind2] - x[ind1], collapse = ", "))
}
And use the function in summarise:
df %>% group_by(name, Utt) %>% summarise(increase = f(value))
Using tidyverse, my solution was similar to yours. One possible modification might be to subset your columns before summing instead of filtering. This will keep all combinations of name and Utt and allow for NA for increase_size in the end. Since the column increase_size is character type, you can convert an empty string to NA.
library(data.table)
library(tidyverse)
df %>%
arrange(name) %>%
group_by(name, Utt) %>%
mutate(diff = c(0, diff(value))) %>%
group_by(grp = rleid(diff < 0), .add = T) %>%
summarise(increase_size = sum(diff[diff > 0], na.rm = T)) %>%
group_by(name, Utt) %>%
summarise(increase_size = toString(increase_size[increase_size > 0])) %>%
mutate(increase_size = na_if(increase_size, ""))
Output
name Utt increase_size
<chr> <chr> <chr>
1 A ah 3.2
2 A oh 1.5, 3.5
3 B ah 3.9
4 B oh NA
I am kind of new to R and programming in general. I am currently strugling with a piece of code for data transformation and hope someone can take a little bit of time to help me.
Below a reproducible exemple :
# Data
a <- c(rnorm(12, 20))
b <- c(rnorm(12, 25))
f1 <- rep(c("X","Y","Z"), each=4) #family
f2 <- rep(x = c(0,1,50,100), 3) #reference and test levels
dt <- data.frame(f1=factor(f1), f2=factor(f2), a,b)
#library loading
library(tidyverse)
Goal : Compute all values (a,b) using a reference value. Calculation should be : a/a_ref with a_ref = a when f2=0 depending on the family (f1 can be X,Y or Z).
I tried to solve this by using this code :
test <- filter(dt, f2!=0) %>% group_by(f1) %>%
mutate("a/a_ref"=a/(filter(dt, f2==0) %>% group_by(f1) %>% distinct(a) %>% pull))
I get :
test results
as you can see a is divided by a_ref. But my script seems to recycle the use of reference values (a_ref) regardless of the family f1.
Do you have any suggestion so A is computed with regard of the family (f1) ?
Thank you for reading !
EDIT
I found a way to do it 'manualy'
filter(dt, f1=="X") %>% mutate("a/a_ref"=a/(filter(dt, f1=="X" & f2==0) %>% distinct(a) %>% pull()))
f1 f2 a b a/a_ref
1 X 0 21.77605 24.53115 1.0000000
2 X 1 20.17327 24.02512 0.9263973
3 X 50 19.81482 25.58103 0.9099366
4 X 100 19.90205 24.66322 0.9139422
the problem is that I'd have to update the code for each variable and family and thus is not a clean way to do it.
# use this to reproduce the same dataset and results
set.seed(5)
# Data
a <- c(rnorm(12, 20))
b <- c(rnorm(12, 25))
f1 <- rep(c("X","Y","Z"), each=4) #family
f2 <- rep(x = c(0,1,50,100), 3) #reference and test levels
dt <- data.frame(f1=factor(f1), f2=factor(f2), a,b)
#library loading
library(tidyverse)
dt %>%
group_by(f1) %>% # for each f1 value
mutate(a_ref = a[f2 == 0], # get the a_ref and add it in each row
"a/a_ref" = a/a_ref) %>% # divide a and a_ref
ungroup() %>% # forget the grouping
filter(f2 != 0) # remove rows where f2 == 0
# # A tibble: 9 x 6
# f1 f2 a b a_ref `a/a_ref`
# <fctr> <fctr> <dbl> <dbl> <dbl> <dbl>
# 1 X 1 21.38436 24.84247 19.15914 1.1161437
# 2 X 50 18.74451 23.92824 19.15914 0.9783583
# 3 X 100 20.07014 24.86101 19.15914 1.0475490
# 4 Y 1 19.39709 22.81603 21.71144 0.8934042
# 5 Y 50 19.52783 25.24082 21.71144 0.8994260
# 6 Y 100 19.36463 24.74064 21.71144 0.8919090
# 7 Z 1 20.13811 25.94187 19.71423 1.0215013
# 8 Z 50 21.22763 26.46796 19.71423 1.0767671
# 9 Z 100 19.19822 25.70676 19.71423 0.9738257
You can do this for more than one variable using:
dt %>%
group_by(f1) %>%
mutate_at(vars(a:b), funs(./.[f2 == 0])) %>%
ungroup()
Or generally use vars(a:z) to use all variables between a and z as long as they are one after the other in your dataset.
Another solution could be using mutate_if like:
dt %>%
group_by(f1) %>%
mutate_if(is.numeric, funs(./.[f2 == 0])) %>%
ungroup()
Where the function will be applied to all numeric variables you have. The variables f1 and f2 will be factor variables, so it just excludes those ones.
This question is similar to selecting the top N values within a group by column here.
However, I want to select the last N values by group, with N depending on the value of a corresponding count column. The count represents the number of occurrences of a specific name. If count >3, I only want the last three entries but if it is less than 3, I only want the last entry.
# Sample data
df <- data.frame(Name = c("x","x","x","x","y","y","y","z","z"), Value = c(1,2,3,4,5,6,7,8,9))
# Obtain count for each name
count <- df %>%
group_by(Name) %>%
summarise(Count = n_distinct(Value))
# Merge dataframe with count
merge(df, count, by=c("Name"))
# Delete the first entry for x and the first entry for z
# Desired output
data.frame(Name = c("x","x","x","y","y","y","z"), Value = c(2,3,4,5,6,7,9))
Another dplyrish way:
df %>% group_by(Name) %>% slice(tail(row_number(),
if (n_distinct(Value) < 3) 1 else 3
))
# A tibble: 7 x 2
# Groups: Name [3]
Name Value
<fctr> <dbl>
1 x 2
2 x 3
3 x 4
4 y 5
5 y 6
6 y 7
7 z 9
The analogue in data.table is...
library(data.table)
setDT(df)
df[, tail(.SD, if (uniqueN(Value) < 3) 1 else 3), by=Name]
The closest thing in base R is...
with(df, {
len = tapply(Value, Name, FUN = length)
nv = tapply(Value, Name, FUN = function(x) length(unique(x)))
df[ sequence(len) > rep(nv - ifelse(nv < 3, 1, 3), len), ]
})
... which is way more difficult to come up with than it should be.
Another possibility:
library(tidyverse)
df %>%
split(.$Name) %>%
map_df(~ if (n_distinct(.x) >= 3) tail(.x, 3) else tail(.x, 1))
Which gives:
# Name Value
#1 x 2
#2 x 3
#3 x 4
#4 y 5
#5 y 6
#6 y 7
#7 z 9
In base R, split the df by df$Name first. Then, for each subgroup, check number of rows and extract last 3 or last 1 row conditionally.
do.call(rbind, lapply(split(df, df$Name), function(a)
a[tail(sequence(NROW(a)), c(3,1)[(NROW(a) < 3) + 1]),]))
Or
do.call(rbind, lapply(split(df, df$Name), function(a)
a[tail(sequence(NROW(a)), ifelse(NROW(a) < 3, 1, 3)),]))
# Name Value
#x.2 x 2
#x.3 x 3
#x.4 x 4
#y.5 y 5
#y.6 y 6
#y.7 y 7
#z z 9
For three conditional values
do.call(rbind, lapply(split(df, df$Name), function(a)
a[tail(sequence(NROW(a)), ifelse(NROW(a) >= 6, 6, ifelse(NROW(a) >= 3, 3, 1))),]))
If you're already using dplyr, the natural approach is:
library(dplyr)
# Sample data
df <- data.frame(Name = c("x","x","x","x","y","y","y","z","z"),
Value = c(1,2,3,4,5,6,7,8,9))
df %>%
group_by(Name) %>%
mutate(Count = n_distinct(Value),
Rank = dense_rank(desc(Value))) %>%
filter((Count>= 3 & Rank <= 3) | (Rank==1)) %>%
select(-c(Count,Rank))
There's no need for a merge since you are just counting and ranking on groups defined by Name. Then, you apply a filter on your count and rank requirements, and (optionally, for clean-up) drop the counts and ranks.
Starting with data containing multiple observations for each group, like this:
set.seed(1)
my.df <- data.frame(
timepoint = rep(c(0, 1, 2), each= 3),
counts = round(rnorm(9, 50, 10), 0)
)
> my.df
timepoint counts
1 0 44
2 0 52
3 0 42
4 1 66
5 1 53
6 1 42
7 2 55
8 2 57
9 2 56
To perform a summary calculation at each timepoint relative to timepoint == 0, for each group I need to pass a vector of counts for timepoint == 0 and a vector of counts for the group (e.g. timepoint == 0) to an arbitrary function, e.g.
NonsenseFunction <- function(x, y){
(mean(x) - mean(y)) / (1 - mean(y))
}
I can get the required output from this table, either with dplyr:
library(dplyr)
my.df %>%
group_by(timepoint) %>%
mutate(rep = paste0("r", 1:n())) %>%
left_join(x = ., y = filter(., timepoint == 0), by = "rep") %>%
group_by(timepoint.x) %>%
summarise(result = NonsenseFunction(counts.x, counts.y))
or data.table:
library(data.table)
my.dt <- data.table(my.df)
my.dt[, rep := paste0("r", 1:length(counts)), by = timepoint]
merge(my.dt, my.dt[timepoint == 0], by = "rep", all = TRUE)[
, NonsenseFunction(counts.x, counts.y), by = timepoint.x]
This only works if the number of observations between groups is the same. Anyway, the observations aren't matched, so using the temporary rep variable seems hacky.
For a more general case, where I need to pass vectors of the baseline values and the group's values to an arbitrary (more complicated) function, is there an idiomatic data.table or dplyr way of doing so with a grouped operation for all groups?
Here's the straightforward data.table approach:
my.dt[, f(counts, my.dt[timepoint==0, counts]), by=timepoint]
This probably grabs my.dt[timepoint==0, counts] again and again, for each group. You could instead save that value ahead of time:
v = my.dt[timepoint==0, counts]
my.dt[, f(counts, v), by=timepoint]
... or if you don't want to add v to the environment, maybe
with(list(v = my.dt[timepoint==0, counts]),
my.dt[, f(counts, v), by=timepoint]
)
You could give the second argument to use the vector from your group of interest as a constant.
my.df %>%
group_by(timepoint) %>%
mutate(response = NonsenseFunction(counts, my.df$counts[my.df$timepoint == 0]))
Or if you want to make it beforehand:
constant = = my.df$counts[my.df$timepoint == 0]
my.df %>%
group_by(timepoint) %>%
mutate(response = NonsenseFunction(counts, constant))
You can try,
library(dplyr)
my.df %>%
mutate(new = mean(counts[timepoint == 0])) %>%
group_by(timepoint) %>%
summarise(result = NonsenseFunction(counts, new))
# A tibble: 3 × 2
# timepoint result
# <dbl> <dbl>
#1 0 0.0000000
#2 1 0.1398601
#3 2 0.2097902