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52 lines
1.2 KiB
R
52 lines
1.2 KiB
R
# Goal: Associative arrays (as in awk) or hashes (as in perl).
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# Or, more generally, adventures in R addressing.
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# Here's a plain R vector:
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x <- c(2,3,7,9)
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# But now I tag every elem with labels:
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names(x) <- c("kal","sho","sad","aja")
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# Associative array operations:
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x["kal"] <- 12
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# Pretty printing the entire associative array:
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x
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# This works for matrices too:
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m <- matrix(runif(10), nrow=5)
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rownames(m) <- c("violet","indigo","blue","green","yellow")
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colnames(m) <- c("Asia","Africa")
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# The full matrix --
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m
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# Or even better --
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library(xtable)
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xtable(m)
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# Now address symbolically --
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m[,"Africa"]
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m["indigo",]
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m["indigo","Africa"]
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# The "in" operator, as in awk --
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for (colour in c("yellow", "orange", "red")) {
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if (colour %in% rownames(m)) {
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cat("For Africa and ", colour, " we have ", m[colour, "Africa"], "\n")
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} else {
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cat("Colour ", colour, " does not exist in the hash.\n")
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}
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}
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# This works for data frames also --
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D <- data.frame(m)
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D
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# Look closely at what happened --
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str(D) # The colours are the rownames(D).
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# Operations --
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D$Africa
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D[,"Africa"]
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D["yellow",]
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# or
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subset(D, rownames(D)=="yellow")
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colnames(D) <- c("Antarctica","America")
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D
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D$America |