Created
June 25, 2024 18:45
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One way to age match using k-nearest neighbors
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library(nabor) | |
# suppose you have two vectors of propensity scores | |
propensity_scores1 <- c(0.1, 0.2, 0.3, 0.4, 0.5) #more controls | |
propensity_scores2 <- c(0.15, 0.25, 0.35) #fewer cases | |
# use the knn function from the nabor package to find the index of the closest match in propensity_scores2 for each score in propensity_scores1 | |
matches <- nabor::knn(matrix(propensity_scores2), matrix(propensity_scores1), k = 1)$nn.idx | |
# print the matches | |
print(matches) | |
# select only one of each nearest match from propensity_scores1 | |
propensity_scores1[!duplicated(matches)] | |
# try a more realistic example | |
ages1 <- sample(30:80, 100, replace = TRUE) | |
ages2 <- sample(50:80, 30, replace = TRUE) | |
# make an overlapping density plot of age1 and age2 | |
plot(density(ages1), col = "red", xlim = c(30, 70), ylim = c(0, 0.05), | |
main = "Age Distribution", xlab = "Age", ylab = "Density") | |
lines(density(ages2), col = "black") | |
# use the knn function from the nabor package to find the index of the closest match in ages2 for each age in ages1 | |
matches <- nabor::knn(matrix(ages2), matrix(ages1), k = 1)$nn.idx | |
# select only one of each nearest match from ages1 | |
ages1_matched <- ages1[!duplicated(matches)] | |
matches <- nabor::knn(matrix(ages1_matched), matrix(ages2), k = 1)$nn.idx | |
ages2_matched <- ages2[!duplicated(matches)] | |
plot(density(ages1_matched), col = "red", xlim = c(30, 70), ylim = c(0, 0.05), | |
main = "Age Distribution", xlab = "Age", ylab = "Density") | |
lines(density(ages2_matched), col = "black") |
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Created on 2024-06-25 with reprex v2.1.0