# Comparison function

Object information
Owning palette(s) Comparison palette
Type VI
Requires Basic Development Environment
Icon

The Comparison Express VI compares input items you specify to determine whether values are equal, greater than, less than, and so on.

## Usage

### Dialog Box Options

Parameter Description
Items to Compare Contains the following options:
• Data points—Compares the data points of the signals in Operand 1 to the data points of the signals in Operand 2, the value you specify in Value, or the Constant Value to Compare Against input.
• Timestamps—Compares the initial time stamps (t0) of the signals in Operand 1 to the initial time stamps (t0) of the signals in Operand 2, the value you specify in Value, or the Constant Value to Compare Against input.
• Time between points—Compares the time between points (dt) of the signals in Operand 1 to the time between points (dt) of the signals in Operand 2, the value you specify in Value, or the Constant Value to Compare Against input.
• Number of data points—Compares the number of data points of the signals in Operand 1 to the number of data points of the signals in Operand 2, the value you specify in Value, or the Constant Value to Compare Against input.
• Signal name—Compares the signal names of the signals in Operand 1 to the signal names of the signals in Operand 2, the value you specify in Value, or the Constant Value to Compare Against input. When comparing signal names, you can use wildcards to match strings. You can use the question mark character (?) to match any single character. You can use the asterisk character (*) to match any sequence of zero or more characters.

If you select Signal name, the Comparison Condition section is disabled and set to = Equal.

Compare Condition Contains the following options:
• = Equal—Determines if two inputs are equal. Because all comparison operations are floating-point operations, consider using Equal within tolerance for equality comparisons.
• <> Not equal—Determines if two inputs are unequal.
• > Greater—Determines if the first input is greater than the second input.
• >= Greater or equal—Determines if the first input is greater than or equal to the second input.
• < Less—Determines if the first input is less than the second input.
• <= Less than or equal—Determines if the first input is less than or equal to the second input.
• Equal within tolerance—Determines if the inputs are equal within the tolerance you specify in Tolerance.
• Tolerance—Specifies the level of tolerance to use when determining if an input is Equal within tolerance. The default is 0.01.
• In range—Determines if an input falls in the range Minimum and Maximum specify.
• Out of range—Determines if an input falls out of the range Minimum and Maximum specify.
• Minimum—Specifies the minimum value of the In range and Out of range comparisons. The Express VI includes Minimum in the range. The default is 0.
• Maximum—Specifies the maximum value of the In range and Out of range comparisons. The Express VI includes Maximum in the range. The default is 1.
Comparison Inputs Contains the following options:
• Second signal input—Compares the Operand 1 input of the Express VI to a second signal input as opposed to a value you specify in Value or the Constant Value to Compare Against input. Select this option to include the Operand 2 input on the Express VI. If Operand 1 and Operand 2 are the same size, each item in Operand 1 is compared to the corresponding item in Operand 2. If Operand 1 and Operand 2 are of different sizes, all the items in Operand 1 are compared to the first item in Operand 2.
• Value—Compares the Operand 1 input to a constant value you specify. The default is 0. If you wire the Constant Value to Compare Against input, the VI uses the value that this input specifies instead.
• Point value—Specifies the constant value with which to compare the Operand 1 input. The default is 0.
• Timestamp value—Specifies the timestamp to apply to the signal. This option is available only if you place a checkmark in the Timestamp checkbox.
• Delta time value—Specifies the constant value with which to compare the Operand 1 input. The default is 0.
• Number of points value—Specifies the number of points to compare. The default is 0.
• Signal name value—Specifies the name of the signal.
Result Contains the following options:
• One result per data point—Returns one result per data point. This option is available only when you select Data points from the Items to Compare pull-down menu.
• One result per channel—Returns one result per channel. When you select Data points from the Items to Compare pull-down menu, One result per channel returns 1 only if all data points in the channel pass the specified comparison. If any point fails, it returns 0.
• One result for all channels—Returns one result for all the channels. When you select Data points from the Items to Compare pull-down menu, One result for all channels returns 1 only if all data points in the channels pass the specified comparison. If any point fails, it returns 0.
• Invert result—Inverts the outputs.
Result Name Contains the following option:
• Change Express VI name to name of function—Changes the name of the Express VI on the block diagram to the name of the function you select in the Comparison Condition section of the configuration dialog box.
Input Signal Displays the input signal. If you wire data to the Express VI and run it, Input Signal displays real data. If you close and reopen the Express VI, Input Signal displays sample data until you run the Express VI again.
Result Preview Displays a preview of the measurement. The Result Preview plot indicates the value of the selected measurement with a dotted line. If you wire data to the Express VI and run the VI, Result Preview displays real data. If you close and reopen the Express VI, Result Preview displays sample data until you run the VI again. If the cutoff frequency values are invalid, Result Preview does not display valid data.

### Block Diagram Inputs

Parameter Description
Operand 1 Specifies the first input for comparison.
Operand 2 Specifies the second signal input for comparison. This input is available only when you select Second signal input in the configuration dialog box.
Constant Value to Compare Against Specifies the constant value with which to compare the Operand 1 input. If Constant Value to Compare Against is not wired, the VI uses the Value specified in the configuration dialog box.
error in Describes error conditions that occur before this node runs.

### Block Diagram Outputs

Parameter Description
Result Returns the resulting data based on the configuration of the Express VI.
error in Contains error information. This output provides standard error out functionality.

## History

Version Change(s)