# TERR_Real

In the Spotfire Custom Expressions dialog box, you can select the pre-defined expression `TERR_Real` from the Function list. This expression function invokes the TERR engine to return a vector or a single column data frame of the data type `numeric` , which is converted to a Spotfire column of the corresponding Spotfire data type Real.

The expression function has at least two arguments.
Argument | Argument description
--- | ---
A TERR script. | The TERR script contains the following. A number of variables using the naming convention that Spotfire requires: `input1` to `inputN`, where `inputN` is the highest number of the specified inputs, numbered sequentally. A TERR assignment operator (`<-`) that assigns the results of the TERR evaluation to an object named `output` (also using the naming convention that Spotfire requires).
Spotfire column names. | Passed as additional arguments, these are the data column names that `input1` to `inputN` represent. All columns must be the same length.

The output type is returned from TERR and converted by Spotfire.
Returned by TERR | Converted in Spotfire
--- | ---
A vector or a single column data frame of data type `numeric`. | A column with the same number of rows as the input, and of the data type Real.

## TERR_Real example

This example uses the TERR_PCA_Cars data sample from the Spotfire library. Select four columns (Name, Type, RetailPrice, and DealerCost), and then add a column that calculates a minimum of 5% profit above dealer cost.

    TERR_Real("output <- input1*1.05",[DealerCost]))

The resulting table in Spotfire shows the following.

Important: Spotfire autocorrects the function case or name to that of built-in Spotfire function names. (For example, TERR contains the function `max`, and Spotfire contains the function `Max`. ) You must overwrite this autocorrection manually to ensure that you use the TERR function case and name in your expression function.

See Embedding the Contents of a Script in an Expression Function for a detailed procedure for creating an expression function.