[英]How to DROP columns from ffdf object ? (R)
我可以輕松地刪除ffdf對象的列嗎？
library(ff);library(ffbase)
irisdf=as.ffdf(iris)
如何僅包含Sepal.length和Species列？
您可以嘗試從ffbase subset
library(ffbase)
Subiris <- subset(irisdf, select=c('Sepal.Length', 'Species'))
dim(Subiris)
#[1] 150 2
colnames(Subiris)
#[1] "Sepal.Length" "Species"
library(ff)
irisdf <- as.ffdf(iris)
filename(irisdf)
## Referencing the same data on disk (just making an new virtual ffdf)
example1 <- irisdf[setdiff(colnames(irisdf), c("Sepal.Length", "Species"))]
filename(example1)
## Referencing new data (copying)
example2 <- clone(irisdf[setdiff(colnames(irisdf), c("Sepal.Length", "Species"))])
filename(example2)
如何從函數包ff（在R中）重載函數“[< - 。ffdf”和“[.ffdf”]？
[英]How to overload the functions “[<-.ffdf” and “[.ffdf” from package ff (in R)?
R {ff}：如何在ffdf對象中添加依賴於同一行中其他元素的新列？
[英]R{ff}:How to add a new column which depends on other elements in the same row in ffdf object?
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