Nested If Else Question Not Working in Dataframe

Question

I'm working with a column in a dataframe of numeric data called "L_D" which has a range of values from 0.6-1.9. I'm trying to create a new column that categorizes the range in 3 ranges: "high" for L_D>1.4, "low" for L_D<0.9, or "medium".

#add L/D grouping to CompStrngth, <0.9=Low aspect ratio; >1.4=High Aspect Ratio, else = other raio
ifelse(CompStrngthData$L_D > 1.4, CompStrngthData$L_D_group <- "high",
   ifelse(CompStrngthData$L_D > 0.9, CompStrngthData$L_D_group <- "medium",
        CompStrngthData$L_D_group <- "low" )
)

When I run this code, it produces the desired result in the console. But when I open up the dataframe, it produces a column filled with "low".

Because of that I found the cut function and it works great with the desired results

CompStrngthData$L_D_group <- cut(CompStrngthData$L_D, breaks = c(-Inf,0.9,1.4,Inf), labels = c("low", "medium", "high"))

I'm sure it's a simple mistake I'm overlooking with the dataframe or if else function, just looking to understand my error.

I've never seen a situation where assignment within the yes= or no= arguments of ifelse was a reasonable thing to do. While it is syntactically legal to do so, it's always (imo) been more confusing than not, so like @akrun's answer, I always keep assignments outside of ifelse (nested or otherwise). — r2evans
– r2evans, Commented Mar 29, 2020 at 17:43
Can you dput your data to help reproduce and troubleshoot the issue you are running into? — sachin2014
– sachin2014, Commented Mar 29, 2020 at 17:44

akrun · Accepted Answer · 2020-03-29 17:39:22Z

2

The issue could be with the assignment inside the ifelse, instead, take it outside

CompStrngthData$L_D_group <- ifelse(CompStrngthData$L_D > 1.4,  "high",
    ifelse(CompStrngthData$L_D > 0.9, "medium",
    "low" )
         )

answered Mar 29, 2020 at 17:39

akrun

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1 Comment

Patrick Over a year ago

That is it! Knew it was something simple like that. Though, I much prefer the cut function, especially if I was working with more groupings.

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