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Perform mathematical function
The Math Function block performs numerous common mathematical functions.
Tip To perform square root calculations, use the Sqrt block. |
You can select one of the following functions from the Function parameter list.
Function | Description | Mathematical Expression | MATLAB^{®} Equivalent |
---|---|---|---|
exp | Exponential | e^{u} | exp |
log | Natural logarithm | ln u | log |
10^u | Power of base 10 | 10^{u} | 10.^u |
log10 | Common (base 10) logarithm | log u | log10 |
magnitude^2 | Complex modulus | |u|^{2} | |
square | Power 2 | u^{2} | u.^2 |
pow | Power | u^{v} | power |
conj | Complex conjugate | ū | conj |
reciprocal | Reciprocal | 1/u | 1./u |
hypot | Square root of sum squares | (u^{2}+v^{2})^{0.5} | hypot |
rem | Remainder after division | — | rem |
mod | Modulus after division | — | mod |
transpose | Transpose | u^{T} | u.' |
hermitian | Complex conjugate transpose | u^{H} | u' |
The block output is the result of the operation of the function on the input or inputs. The functions support the following types of operations.
Function | Scalar Operations | Element-Wise Vector and Matrix Operations | Vector and Matrix Operations |
---|---|---|---|
exp | yes | yes | — |
log | yes | yes | — |
10^u | yes | yes | — |
log10 | yes | yes | — |
magnitude^2 | yes | yes | — |
square | yes | yes | — |
pow | yes | yes | — |
conj | yes | yes | — |
reciprocal | yes | yes | — |
hypot | yes, on two inputs | yes, on two inputs (two vectors or two matrices of the same size, a scalar and a vector, or a scalar and a matrix) | — |
rem | yes, on two inputs | yes, on two inputs (two vectors or two matrices of the same size, a scalar and a vector, or a scalar and a matrix) | — |
mod | yes, on two inputs | yes, on two inputs (two vectors or two matrices of the same size, a scalar and a vector, or a scalar and a matrix) | — |
transpose | yes | — | yes |
hermitian | yes | — | yes |
The name of the function appears on the block. The appropriate number of input ports appears automatically.
Tip Use the Math Function block instead of the Fcn block when you want vector or matrix output, because the Fcn block produces only scalar output. |
The following table shows the input data types that each function of the block can support.
Function | single | double | boolean | built-in integer | fixed point |
---|---|---|---|---|---|
exp | yes | yes | — | — | — |
log | yes | yes | — | — | — |
10^u | yes | yes | — | — | — |
log10 | yes | yes | — | — | — |
magnitude^2 | yes | yes | — | yes | yes |
square | yes | yes | — | yes | yes |
pow | yes | yes | — | — | — |
conj | yes | yes | — | yes | yes |
reciprocal | yes | yes | — | yes | yes |
hypot | yes | yes | — | — | — |
rem | yes | yes | — | yes | — |
mod | yes | yes | — | yes | — |
transpose | yes | yes | yes | yes | yes |
hermitian | yes | yes | — | yes | yes |
All supported modes accept both real and complex inputs, except for reciprocal, which does not accept complex fixed-point inputs.
The block output is real or complex, depending on what you select for Output signal type.
The Main pane of the Math Function block dialog box appears as follows:
Specify the mathematical function. See Description for more information about the options for this parameter.
Specify the output signal type of the Math Function block as auto, real, or complex.
Function | Input Signal Type | Output Signal Type | ||
---|---|---|---|---|
Auto | Real | Complex | ||
exp, log, 10u, log10, square, pow, reciprocal, conjugate, transpose, hermitian | real complex | real complex | real error | complex complex |
magnitude squared | real complex | real real | real real | complex complex |
hypot, rem, mod | real complex | real error | real error | complex error |
Specify the time interval between samples. To inherit the sample time, set this parameter to -1. See Specify Sample Time in the online documentation for more information.
The Signal Attributes pane of the Math Function block dialog box appears as follows:
Note Some parameters on this pane are available only when the function you select in the Function parameter supports fixed-point data types. |
Specify the minimum value that the block can output. The default value is [] (unspecified). Simulink^{®} software uses this value to perform:
Simulation range checking (see Signal Ranges)
Automatic scaling of fixed-point data types
Specify the maximum value that the block can output. The default value is [] (unspecified). Simulink software uses this value to perform:
Simulation range checking (see Signal Ranges)
Automatic scaling of fixed-point data types
Specify the output data type. You can set it to:
A rule that inherits a data type, for example, Inherit: Inherit via back propagation
The name of a built-in data type, for example, single
The name of a data type object, for example, a Simulink.NumericType object
An expression that evaluates to a data type, for example, fixdt(1,16,0)
Click the Show data type assistant button to display the Data Type Assistant, which helps you set the Output data type parameter.
See Specify Block Output Data Types for more information.
Select to lock the output data type setting of this block against changes by the Fixed-Point Tool and the Fixed-Point Advisor. For more information, see Use Lock Output Data Type Setting.
Specify the rounding mode for fixed-point operations. For more information, see Rounding. in the Fixed-Point Designer™ documentation.
Action | Reasons for Taking This Action | What Happens for Overflows | Example |
---|---|---|---|
Select this check box. | Your model has possible overflow, and you want explicit saturation protection in the generated code. | Overflows saturate to either the minimum or maximum value that the data type can represent. | The maximum value that the int8 (signed, 8-bit integer) data type can represent is 127. Any block operation result greater than this maximum value causes overflow of the 8-bit integer. With the check box selected, the block output saturates at 127. Similarly, the block output saturates at a minimum output value of -128. |
Do not select this check box. | You want to optimize efficiency of your generated code. You want to avoid overspecifying how a block handles out-of-range signals. For more information, see Checking for Signal Range Errors. | Overflows wrap to the appropriate value that is representable by the data type. | The maximum value that the int8 (signed, 8-bit integer) data type can represent is 127. Any block operation result greater than this maximum value causes overflow of the 8-bit integer. With the check box cleared, the software interprets the overflow-causing value as int8, which can produce an unintended result. For example, a block result of 130 (binary 1000 0010) expressed as int8, is -126. |
When you select this check box, saturation applies to every internal operation on the block, not just the output or result. Usually, the code generation process can detect when overflow is not possible. In this case, the code generator does not produce saturation code.