在施法时保留变量

Question

我正在尝试将一些长数据转换成广泛的数据,但无法弄清楚如何将某些变量附加到唯一的id.以下是我需要它做的事情,除了它删除附加到每个gridNumber的lat和long变量.我想在广泛的时候保留这些.

dput:

df <- structure(list(gridNumber = c("17578", "18982", "18983", "18984", 
"18985", "18986", "18987", "18988", "18989", "18990"), value = c(22.7000007629395, 
22.2900009155273, 22.25, 21.9799995422363, 21.1000003814697, 
20.7700004577637, 20.6200008392334, 20.5699996948242, 20.5699996948242, 
20.5799999237061), lat = c(-95.1249999994964, -95.1666666661633, 
-95.1249999994964, -95.0833333328295, -95.0416666661626, -94.9999999994957, 
-94.9583333328288, -94.9166666661619, -94.874999999495, -94.8333333328281
), long = c(49.4166666666667, 49.375, 49.375, 49.375, 49.375, 
49.375, 49.375, 49.375, 49.375, 49.375), ID = c("PRISM_ppt_stable_4kmM2_190001_bil", 
"PRISM_ppt_stable_4kmM2_190001_bil", "PRISM_ppt_stable_4kmM2_190001_bil", 
"PRISM_ppt_stable_4kmM2_190001_bil", "PRISM_ppt_stable_4kmM2_190001_bil", 
"PRISM_ppt_stable_4kmM2_190001_bil", "PRISM_ppt_stable_4kmM2_190001_bil", 
"PRISM_ppt_stable_4kmM2_190001_bil", "PRISM_ppt_stable_4kmM2_190001_bil", 
"PRISM_ppt_stable_4kmM2_190001_bil")), .Names = c("gridNumber", 
"value", "lat", "long", "ID"), class = c("data.table", "data.frame"
), row.names = c(NA, -10L))

码:

library(data.table)
wide <- dcast.data.table(df, gridNumber~ID, value = 'value')

Answer 1

要解释@Frank评论(和正确答案),演员公式采用表格LHS ~ RHS.LHS是您希望成为行键的列集,对于列中的列也是如此RHS.因此,如果你想保持gridNumber,lat和long作为每个行的唯一键,那么设置LHS为gridNumber + lat + long如下:

wide <- dcast.data.table(df, gridNumber + lat + long ~ ID, value = 'value')

dcast可以用来代替dcast.data.table@Arun所指出的(对于任何版本> = 1.9.6,目前在CRAN上).