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How to get the sum of each four rows of a matrix in R
(3 answers)
Average of n rows
(1 answer)
Closed 8 months ago.
I have a column with hundreds of values, I want to get the average for each 4 rows, then I move to another four rows, etc. How could I write that loop in R studio, I attached here a simple example, what should I do if I have NA values, how to consider those values as zeros?
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R keep rows with at least one column greater than value
(3 answers)
Delete rows in R if a cell contains a value larger than x
(1 answer)
Closed 2 years ago.
I have a matrix, and I want to remove all rows that contain at least one element less than a value, 3 on this example. Sample data:
A=matrix(c(10,2,4,8,5,4,8,10,5),byrow=T,ncol=3)
#Remove rows that contain at least one value less than 3
final_matrix=matrix(c(8,5,4,8,10,5), byrow=T,ncol=3)
How to get to the final matrix from the initial matrix A? My real matrix contains thousands of rows tens of columns, this is a toy example. I tried A=A[A>3,] but I get an error "logical subscript too long"
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How do I split a data frame among columns, say at every nth column?
(1 answer)
What is the algorithm behind R core's `split` function?
(1 answer)
Closed 4 years ago.
I have a data frame that is 640 rows by 50,002 columns. I need to split the data columns 2:50001 into 5 equal groups. I have tried the split and sample commands but it gave an error.
This question already has answers here:
R data.table sum of group subset using dates
(3 answers)
Count rows since a date condition is met
(2 answers)
Count number of rows in window around timestamp
(3 answers)
Closed 4 years ago.
I have some IDs, dates and Values.
I want to sum values for each ID for the last 10 days.
This code can reproduce my dataset:
date<-as.Date(c("05/03/2017","05/10/2017","05/14/2017","05/19/2017","05/22/2017"),format="%m/%d/%Y")
value<-rpois(20,50)
id<-NULL
for(i in 1:4){id<-c(id,rep(i,5))}
mydata<-data.frame(id,date=rep(date,4),value)
So, the output would be the dataset above with a new column. This column would have the sum of values of lasts 10 days.
Thanks in advance.
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Extracting specific columns from a data frame
(10 answers)
Closed 4 years ago.
in R programming, how do I subset a matrix so that I can skip columns in between? I only know how to do it continuously such as 1:4, but what if I want the first, second, and fourth colum
You can select specific columns as follows:
new_df <- x[,c(1,2,4)]# Select column 1,2 and 4
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How to get all possible combinations of n number of data set?
(2 answers)
How to calculate combination and permutation in R?
(6 answers)
Closed 5 years ago.
I am getting a tough time in selecting the combinations of factors.
I have a vector as ("Ryan", "Leo", "Jack","Harry","Edd").
I want to get the list of of all combinations taken 3 of the names once.
I want to do it in R. Probably a resultant matrix will help me.
We can use combn
t(combn(vec1, 3))