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Melt reshape decast long data short data length conversion data cleaning row column conversion

2022-04-23 13:01:00 【qq_ fifty-two million eight hundred and thirteen thousand one h】

melt reshape decast Long data short data Long short conversion Data cleaning Transformation of ranks 

# examples from 'tidyr' package

library(tidyr)
library(reshape2)

stocks = data.frame(
  time = as.Date('2009-01-01') + 0:9,
  X = rnorm(10, 0, 1),
  Y = rnorm(10, 0, 2),
  Z = rnorm(10, 0, 4)
)
head(stocks)

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stocksm = stocks %>%
  melt(id.vars = "time", variable.name = "stock", value.name = "price")
head(stocksm)
table(stocksm$stock)

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stocksm %>% dcast(time ~ stock)

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stocksm %>% dcast(stock ~ time)

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# dcast and melt are complements
df = data.frame(x = c("a", "b"), y = c(3, 4), z = c(5, 6))

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df %>%
  dcast(z ~ x, value.var = "y") %>%
  melt(id.vars = "z", variable.name = "x", value.name = "y", na.rm = TRUE)
# }

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