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Editorial Team
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Asked: 2026-06-11T15:30:17+00:00

I’m trying to convert three character variables in a data frame to factors, and

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I’m trying to convert three character variables in a data frame to factors, and I keep getting an error for one of the three. The problematic variable, fund.category, has 4 possible values: “Undefined”, “Small”, “Large Existing”, and “Large New Construction”. My code follows – I first read the data frame from an excel sheet using XLConnect, then dropped unnecessary variables and renamed the ones that I kept:

a.projects <- readWorksheet(wb, sheet = "ProjectsDetail")
a.projects.2 <- a.projects[c("ProjectNumber", "BusinessType", "Fund.Category")]
a.projects.2 <- rename(a.projects.2,
                       c("ProjectNumber" = "project.number",
                         "BusinessType" = "business.type",
                         "Fund.Category" = "fund.catetgory"))
str(a.projects.2)
a.projects.2$project.number <- as.factor(a.projects.2$project.number)
a.projects.2$business.type <- as.factor(a.projects.2$business.type)   
a.projects.2$fund.category <- as.factor(a.projects.2$fund.category)

Here is the structure of a.projects.2, produced before I tried to do the factor conversions:

'data.frame':   4291 obs. of  3 variables:
 $ project.number: chr  "APS-10-02825" "APS-10-02826" "APS-10-02876" "APS-10-03134" ...
 $ business.type : chr  "Office" "Office" "Process Industrial" "K-12 School" ...
 $ fund.catetgory: chr  "Undefined" "Undefined" "Large Existing" "Large New Construction" ...

And here is the error from the console:

a.projects.2$fund.category <- as.factor(a.projects.2$fund.category)

Error in `$<-.data.frame`(`*tmp*`, "fund.category", value = integer(0)) : 
replacement has 0 rows, data has 4291

The same code produced no errors for my other two character variables (project.number and business.type). Any ideas why this isn’t working?

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1 Answer

  1. Editorial Team

    You have misspelled “fund.category” in your earlier statement:

    a.projects.2 <- rename(a.projects.2,
                       c("ProjectNumber" = "project.number",
                         "BusinessType" = "business.type",
                         "Fund.Category" = "fund.catetgory"))

    Fix the typo and it should be happy 🙂

    To understand the error,

    a.projects.2$fund.category returns NULL

    as.factor(NULL) returns factor(0)

    and it is when assigning factor(0) to a.projects.2$fund.category that you get the error:

    Error in `$<-.data.frame`(`*tmp*`, "fund.category", value = integer(0)) : 
replacement has 0 rows, data has 4291
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