The = Command

Command Summary

Returns true if value1 is equal to value2.

Command Syntax

value1=value2

Menu Location

Press:

1. 2nd TEST to access the test menu.
2. 1 to select =, or use arrows.

Calculator Compatibility

TI-83/84/+/SE

Token Size

1 byte

The = (equal) operator takes two numbers, variables, or expressions, and tests to see if they are equal to each other. It will return 1 if they are, and 0 if they are not. When determining the order of operations, = will be executed after the math operators, but it will be executed before the logical operators and in the order that it appears from left to right with the other relational operators.

1=0
           0
0->X
           0
3→Y
           3
X=Y
           0

Precision

The TI-84+ calculator appears to round numbers to 10 significant digits when checking for equality (even though behind the scenes in memory numbers are stored up to 14 digits). So for example:

0.99999999999=1       // True  (11 digits get rounded to 10)
0.9999999999=1        // False (with 10 digits not rounded)
99999.999999=100000   // True  (11 digits get rounded to 10)
99999.99999=100000    // False (with 10 digits not rounded)

Advanced Uses

Just like the other relational operators, = can take real numbers and lists for variables. In order to compare the lists, however, both must have the same dimensions; if they don't, the calculator will throw a ERR:DIM MISMATCH error. When comparing a real number to a list, the calculator will actually compare the number against each element in the list and return a list of 1s and 0s accordingly.

{2,4,6,8}={1,3,5,7
           {0 0 0 0}
5={1,2,3,4,5
           {0 0 0 0 1}

Besides real numbers and lists, = also allows you compare strings, matrices, and complex numbers. However, the variables must be of the same type, otherwise the calculator will throw a ERR:DATA TYPE error.

[[1,2,3]]=[[1,2,3
                      1
"HELLO"="WORLD
                      0
(3+4i)=(5-2i)
                      0

When matrices are compared, the result is 1 if the matrices are identical. Both matrices must have the same dimensions, otherwise you will get a ERR:DIM MISMATCH error. Internally, the calculator compares values from the bottom right of each matrix, moving left across each row from bottom to top. If unequal elements are found, the calculator returns 0 without examining the rest of the matrix.

Optimization

When a variable is used in a conditional statement, and the only values that are possible for a variable are 1 and 0, you can get rid of the = sign and simply use the variable by itself.

:If X=1
can be
:If X

Error Conditions

• ERR:DATA TYPE is thrown if you try to compare two different kinds of variables, such as a string and number or a list and matrix.
• ERR:DIM MISMATCH is thrown if you try to compare two lists or matrices that have different dimensions.

Related Commands

• ≠ (not equal)
• > (greater than)
• ≥ (greater than equal)
• < (less than)
• ≤ (less than equal)

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