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Variables

Variables in MedCalc may be basic variables, which refer directly to columns in the data table or can be a combination of variables or a transformation of a variable.

1. The basic variable: column heading

These variables refer directly to columns in the data table.

  • The name of the variable is the heading you enter for the column in the data table.
  • A variable name should not include any spaces, nor the following characters: - + / * = < > # & $ | ^ : , ; . ( ) ' " [ ] { }.
  • The variable name should not start with a number and it must be different from reserved words such as TRUE, FALSE, ROW and COLUMN.
  • The variable name should not be equal to the address of a spreadsheet cell such as A1, S1, AB35, IL6, etc.

2. Combination of variables

A mathematical formula combining two or more variables.

For example: WEIGHT/(HEIGHT*HEIGHT)

Any of the following operators can be used to combine variables (in order of precedence):

^Exponentiation
-Negation
* /Multiplication, Division
+ -Addition, subtraction

As shown in the example, brackets can be used to change the operators precedence.

3. Transformation of a variable

When a variable needs transformation, you can use one of the many MedCalc spreadsheet functions. For example, if a variable needs square root transformation you use the SQRT(variable) function as new variable.

How to create a derived variable

The example file ExampleFile2 contains data on body weight (in kg) and length (in m). You want to have a new variable Body Mass Index which is the weight divided by length squared.

Click Data in the MedCalc.net menu. Next click Variables. The browser displays the variables in the data table.

Variables

Click the New variable hyperlink. A new input panel is displayed which you complete as follows:

Variables

Click Save and the new variable is added to the variables list:

Variables

See also