user3032689 - 1 year ago 70
R Question

# Delete duplicates in large dataset based on condition

I would like to delete duplicates in a very large dataset (millions of rows) based on a condition. I thought about the following simplifying example to illustrate my prob:

``````test <- read.table(
text = "
ID  YEAR  Count Value
A   1900    1   10
A   1900    2   9
A   1900    3   8
A   1900    4   7
A   1900    5   6
A   1900    6   5
A   1900    7   4
A   1900    7   10
A   1900    7   9
A   1900    8   3
A   1900    8   10
A   1900    8   9
A   2000    1   10
A   2000    2   9
A   2000    3   8
A   2000    3   10
A   2000    3   9
B   1800    1   10
B   1800    2   9
B   1800    3   8
B   1800    3   10
B   1800    3   9
B   1800    4   7
B   1900    1   10
B   1900    2   9
B   1900    2   10
B   1900    2   9
library(data.table)
setDT(test)
``````

In this simplified dataset, I have two individuals (A and B), for different but possibly overlapping years. A Count is given, as well as a value.

I would like to delete the observations for each ID within each YEAR and Count group, that are duplicates and fullfill a certain condition (see below). For example for the group:

``````A   1900    7   4
A   1900    7   10
A   1900    7   9
``````

I would like to delete all observations, whose value is larger than the minimum value within each group. In this case I would like to have only

``````A   1900    7   4
``````

as a remainder.

Note that my real dataset is very large and has many more columns. Therefore if possible, I am looking for a solution which is memory-efficient.

I hope that was clear enough. If not, feel free to ask for any information that is missing.

In R, you can answer this with the following: `test[,.(Value=min(Value)), by=.(ID, Year, Count)]`

Here we are going through the data and finding the minimum value for each combination of ID, Year, and Count. This uses the data.table syntax from the package data.table

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