# Enter a Formula for an Attribute

**Entering and Editing a Formula**

Briefly, click on an attribute name in a case table and choose **Edit Formula** to open the formula editor. Enter the formula for the attribute there.

To calculate the values of an attribute from the values of other attributes, write a formula telling CODAP how to do the calculation.

For example, if your student data has height expressed as two attributes, feet and inches, you might write a formula for *heightInInches*, which would be 12 * *feet* + *inches*. If you had *time* and *distance*, you might make *speed*.

You write the formula in the formula editor. A formula is not a complete equation; it is an expression for computing the value of an attribute. We’ll use the example in which we define speed to be *distance/time*.

- Make a new attribute to hold your calculated values (click on the plus sign on the top right of the table to add a new attribute).
- In a case table for the collection, click the attribute name and choose
**Edit Formula**. The formula editor appears. - Enter the formula. Type just the right side;
**no equals signs**. Use the asterisk (“*”) for multiplication and the slash (“/”) for division. Click on the**Insert Value**button and select an attribute by name to insert into the formula. For our example, to get speed, click on “Insert Value,” select “distance,” type in the slash (“/”), then click “Insert Value” and select “time.” There’s a lot you can do with this editor. To find possible formulas you can use and insert into the formula editor, click on the**Insert Function**button. Click on the name of the formula to insert it into the editor. You can click on the**i**to the right of a formula

name to learn more about how to use the formula.

- Click
**Apply**to close the formula editor. You should see the new values in the table column.

**Using Operators**

*Arithmetic operators*: Addition (+), subtraction (–), multiplication (*), division (/ or ÷), modulo (%) and exponentiation (^) all respect the usual rules of algebra. So 3 + 4 * 5 = 23, and 3^2 – 6 / 2 = 6.

*Comparison operators*

- = (equals): “a” = “b” is
*false* - != (not equals): 4 != 5 is
*true*. (Can also use ≠.) - < (less than), <= (less than or equals), > (greater than) and >= (greater than or equals): 7 + 2 <= 9 is
*true*. (Can also use ≤ and ≥.) - & (logical and): 3+2=5 & 4+3=7 returns
*true*. (Can also use “and” and “AND”.) - | (logical or): “a”=”b” | “a” = “a” is
*true*. (Can also use “or” and “OR”.)

*Additional resources*