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I am using information from a base data.table to pull data from other data.tables as in the following example:

test <- function() {
    library(data.table)

    test.dt <-     data.table(id=c("abc","xyz","ijk"),type=c("1","1","0"),line.position=1:3)
    counts.dt <- data.table(
            abc=c(10,NA,NA,NA),xyz=c(20,30,NA,NA),ijk=c(10,10,10,10),X2abc=NA,X3abc=1:4)

    print(test.dt)
    print(counts.dt)
    test.dt[,count:=sum(!is.na(counts.dt[[id]])),by=id]
    test.dt[,count.value:=counts.dt[line.position,id,with=FALSE],by=id]
    print(test.dt)
}

This works fine, and returns the expected result: a column that pulls uses (line.position,id) from a row in test.dt to grab values of counts(line.position,id).

However, I cannot repeat this with a more complex example that pulls data from a worksheet. I get the error: Error in Math.factor(j) : abs not meaningful for factors. This error is thrown right before the last print statement. 

test2 <- function(
    file.directory="C:/Users/csnyder/Desktop/BootMethod/",
    file.name="test.xlsx",  
    resample.number=3
    )

{
    require("PBSmapping")
    require("xlsx")
    library(data.table)

    #Load input sheets
    file.path<-sprintf("%s%s",file.directory,file.name)
    excel.data<-read.xlsx(file.path,sheetIndex=1,header=TRUE,stringsAsFactors=TRUE)
    data.DT<-data.table(excel.data)
    excel.data<-read.xlsx(file.path,sheetIndex=2,header=TRUE,stringsAsFactors=TRUE)
    base.DT<-data.table(excel.data)
    excel.data<-read.xlsx(file.path,sheetIndex=3,header=TRUE,stringsAsFactors=TRUE)
    related.DT<-data.table(excel.data)
    excel.data<-NULL

    #add max rows to each ID type. with=TRUE, colnames used as variables.
    #get.text<-function(x){return(as.character(x))}
    base.DT<-base.DT[,Max.Sample:= sum(!is.na(data.DT[[ID]]),na.rm=TRUE),by=ID]

    base.length<-nrow(base.DT)
    base.DT[,Sub.Number:=1:base.length]
    base.DT[,Resample:=1]
    resample.base.DT<-base.DT

    #Add line numbers to data tables.
    data.DT[,Line:=1:nrow(data.DT)]
    related.DT[,Line:=1:nrow(related.DT)]

    #resample number added to base DT, then will make a for loop by resample numbers             and loop it.
    for(counter in 1:resample.number){
        base.DT<-rbindlist(list(base.DT,resample.base.DT[,Resample:=counter]))
    }
    #remove loop initiator
    base.DT<-base.DT[-(1:base.length)]
    #number rows
    base.DT[,Row.Number:=Resample*base.length+Sub.Number-base.length]

    #pick line to sample
    pick.row<-function(x){return(runif(1,1,x))}
    base.DT[,"Line":=runif(1,1,Max.Sample),with=FALSE]
    base.DT[,"Line":=round(runif(1,1,Max.Sample),digits=0),by=Row.Number]

    #Pull cell from data.DT (and related.DT) that has position corresponding to the         matching Row.Number and ID in base.DT
    base.DT[,From.Data:=data.DT[Line,ID,with=FALSE],by=ID]
    print(base.DT)
}

Now, the sheets from my excel workbook import what looks like (to me at least) the following:

Sheet1:

data.DT<-data.table(item1=c("AAAA","2XXX",780,684,614,39),item2=c("AAAA","XXX",10,314,NA,NA))

Sheet2:

base.DT<-data.table(ID=c("item1","item2"),Level=c("X2XXX","XXX"),Type=c("AAAA","AAAA"),P=c(1000,1000    ),Cat=c("AAAA","AAAA"),Day=c(NA,1))

Sheet3: 

related.DT<-data.table(item1=c("AAAA","2XXX",1,1,1,NA),item2=c("AAAA","XXX",1,1,NA,NA))

At my current location, I can't upload a workbook. Replacing the excel imports with the direct calls above seems to fix the problem. At risk of not having a reproducible question, I have to ask: Has anyone run into this problem or have an idea of how to resolve it? Or perhaps I'm going about this in a convoluted way--work-arounds are equally welcomed! If an excel workbook is needed to fully understand my question, let me know and I'll try my best to upload one.

4

1 回答 1

6

这是一个人得到这个错误的时候：

abs(as.factor(5))
# Error in Math.factor(as.factor(5)) : abs not meaningful for factors

你有因素是因为stringsAsFactors = TRUE在你read的 's 中，并且因为你认为是所有数字的一列中的一个或多个元素实际上不是数字，而是一个字符串。通过运行检查哪些列是因子

sapply(dt, class)

并从那里拿走。

从 Arun 编辑：您应该注意，在将5fromfactor转换为数字时，您应该首先使用将其转换为字符as.character，然后使用as.numericor将其转换为数字或整数as.integer：

x <- factor(5)

# correct conversion
as.numeric(as.character(x))
# [1] 5

# incorrect conversion if you want the number coerced to numeric type
as.numeric(x) # gets the levels of factor numeric instead
# [1] 1
于 2013-04-19T21:30:15.733 回答