[[Fixed] Error in Eval(Predvars, Data, Env) : Numeric ‘Envir’ Arg Not Of Length One

You will encounter error messages while programming. An error message from the modeling data set is shown here. It is a problem with data formatting for the predict() function.

When Can This Error Occur?

The error occurs when data is entered incorrectly into the predict() function. This function is used to predict the outcomes of a model based on your data. There are three parameters to the predict() function. A model, a data frame, and an optional interval parameter.

The model is, of course, the model under test. The data frame contains the information that will be used to test the model. The interval computes a range with a 95% confidence interval. Here’s a piece of code that demonstrates the issue.

# source: error in eval(predvars, data, env) : numeric 'envir' arg not of length one 
> df = read.table(text = '
 +       TRip   Distance  Duration
 + 1     "#3"  2027.072  081.082
 + 2     "#4"  3476.802  139.072
 + 3     "#5"  4622.174  184.886
 + 4     "#6"  4214.416  168.576
 + 5     "#7"  6553.586  262.143
 + 6     "#8"  7123.162  284.926
 + 7     "#9"  7987.369  319.494', header=TRUE)
 > 
 > model = lm(df$Duration ~ df$Distance)
 > 
 > x = predict(model, df$Distance)
   Error in eval(predvars, data, env) : numeric 'envir' arg not of length one

Running this code results in the error message, and the issue can be traced back to using “df$Distance” directly in the predict() function when the data frame is not present.

Why Does This Error Occur?

• The predict() function is looking for a data frame in the second position, but “df$Distance” is simply a vector produced by extracting the second column from the data frames “df,” so you are entering the wrong type of data, which causes the function to return an error message.
• In other words, you are passing incorrectly formatted data to the function, and it responds by telling you that it cannot do it. Unfortunately, as with many error messages, the precise wording is not always helpful.

How To Fix This Error?

Fixing this error is as simple as converting vector “df$Distance” into a data frame that the predict() function will accept. This is possible both inside and outside of the predict() function. Here is a redo of our example code, entered correctly to avoid the error.

# solution: error in eval(predvars, data, env) : numeric 'envir' arg not of length one  
> df = read.table(text = '
 +       TRip   Distance  Duration
 + 1     "#3"  2027.072  081.082
 + 2     "#4"  3476.802  139.072
 + 3     "#5"  4622.174  184.886
 + 4     "#6"  4214.416  168.576
 + 5     "#7"  6553.586  262.143
 + 6     "#8"  7123.162  284.926
 + 7     "#9"  7987.369  319.494', header=TRUE)
 > 
 > model = lm(df$Duration ~ df$Distance)
 >x = predict(model, data.frame(df$Distance))

The fact that “df$Distance” is passed through the data.frame() function distinguishes this version from the one that generates the error message.

> predict(model, df$Distance)
> predict(model, data.frame(df$Distance))

The key difference here is the addition of the data.frame() function.

Also read:- [Fixed] Error: ‘\u’ Used Without Hex Digits In Character String Starting “”c:\u”

Conclusion

We hope you found this quick tutorial on the error in eval(predvars useful, and we encourage you to explore the rest of our website as we have even more guides related to the R language along with a lot of other content you might find interesting.

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