Documentation 
Find maximum values in input or sequence of inputs
The 2D Maximum block identifies the value and/or position of the smallest element in each row or column of the input, or along a specified dimension of the input. The 2D Maximum block can also track the maximum values in a sequence of inputs over a period of time.
The 2D Maximum block supports real and complex floatingpoint, fixedpoint, and Boolean inputs. Real fixedpoint inputs can be either signed or unsigned, while complex fixedpoint inputs must be signed. The output data type of the maximum values match the data type of the input. The block outputs double index values, when the input is double, and uint32 otherwise.
Port  Input/Output  Supported Data Types 

Input  Scalar, vector or matrix of intensity values 

Rst  Scalar value 

Val  Maximum value output based on the Value Mode 

Idx  Onebased output location of the maximum value based on the Index Mode 

When you set the Mode parameter to Value, the block computes the maximum value in each row or column of the input, along vectors of a specified dimension of the input, or of the entire input at each sample time, and outputs the array y. Each element in y is the maximum value in the corresponding column, row, vector, or entire input. The output y depends on the setting of the Find the maximum value over parameter. For example, consider a 3dimensional input signal of size MbyNbyP:
Each row — The output at each sample time consists of an Mby1byP array, where each element contains the maximum value of each vector over the second dimension of the input. For an MbyN input matrix, the block outputs an Mby1 column vector at each sample time.
Each column — The output at each sample time consists of a 1byNbyP array, where each element contains the maximum value of each vector over the first dimension of the input. For an MbyN input matrix, the block outputs a 1byN row vector at each sample time.
In this mode, the block treats lengthM unoriented vector inputs as Mby1 column vectors.
Entire input — The output at each sample time is a scalar that contains the maximum value in the MbyNbyP input matrix.
Specified dimension — The output at each sample time depends on Dimension. When you set Dimension to 1, the block output is the same as when you select Each column. When you set Dimension to 2, the block output is the same as when you select Each row. When you set Dimension to 3, the block outputs an MbyN matrix containing the maximum value of each vector over the third dimension of the input, at each sample time.
For complex inputs, the block selects the value in each row or column of the input, along vectors of a specified dimension of the input, or of the entire input that has the maximum magnitude squared as shown below. For complex value $$u=a+bi$$, the magnitude squared is $${a}^{2}+{b}^{2}$$.
When you set the Mode parameter to Index, the block computes the maximum value in each row or column of the input, along vectors of a specified dimension of the input, or of the entire input, and outputs the index array I. Each element in I is an integer indexing the maximum value in the corresponding column, row, vector, or entire input. The output I depends on the setting of the Find the maximum value over parameter. For example, consider a 3dimensional input signal of size MbyNbyP:
Each row — The output at each sample time consists of an Mby1byP array, where each element contains the index of the maximum value of each vector over the second dimension of the input. For an input that is an MbyN matrix, the output at each sample time is an Mby1 column vector.
Each column — The output at each sample time consists of a 1byNbyP array, where each element contains the index of the maximum value of each vector over the first dimension of the input. For an input that is an MbyN matrix, the output at each sample time is a 1byN row vector.
In this mode, the block treats lengthM unoriented vector inputs as Mby1 column vectors.
Entire input — The output at each sample time is a 1by3 vector that contains the location of the maximum value in the MbyNbyP input matrix. For an input that is an MbyN matrix, the output will be a 1by2 vector of onebased [x y] location coordinates for the maximum value.
Specified dimension — The output at each sample time depends on Dimension. If Dimension is set to 1, the output is the same as when you select Each column. If Dimension is set to 2, the output is the same as when you select Each row. If Dimension is set to 3, the output at each sample time is an MbyN matrix containing the indices of the maximum values of each vector over the third dimension of the input.
When a maximum value occurs more than once, the computed index corresponds to the first occurrence. For example, when the input is the column vector [3 2 1 2 3]', the computed onebased index of the maximum value is 1 rather than 5 when Each column is selected.
When inputs to the block are doubleprecision values, the index values are doubleprecision values. Otherwise, the index values are 32bit unsigned integer values.
When you set the Mode parameter to Value and Index, the block outputs both the maxima and the indices.
When you set the Mode parameter to Running, the block tracks the maximum value of each channel in a time sequence of MbyN inputs. In this mode, the block treats each element as a channel.
The block resets the running maximum whenever a reset event is detected at the optional Rst port. The reset sample time must be a positive integer multiple of the input sample time.
You specify the reset event in the Reset port menu:
None — Disables the Rst port.
Rising edge — Triggers a reset operation when the Rst input does one of the following:
Rises from a negative value to a positive value or zero
Rises from zero to a positive value, where the rise is not a continuation of a rise from a negative value to zero (see the following figure)
Falling edge — Triggers a reset operation when the Rst input does one of the following:
Falls from a positive value to a negative value or zero
Falls from zero to a negative value, where the fall is not a continuation of a fall from a positive value to zero (see the following figure)
Either edge — Triggers a reset operation when the Rst input is a Rising edge or Falling edge (as described above)
Nonzero sample — Triggers a reset operation at each sample time that the Rst input is not zero
To calculate the statistical value within a particular region of interest (ROI) of the input, select the Enable ROI processing check box. This applies to any mode other than running mode and when you set the Find the maximum value over parameter to Entire input and you select the Enable ROI processing check box. ROI processing applies only for 2D inputs.
You can specify a rectangle, line, label matrix, or binary mask ROI type.
Use the binary mask to specify which pixels to highlight or select.
Use the label matrix to label regions. Pixels set to 0 represent the background. Pixels set to 1 represent the first object, pixels set to 2, represent the second object, and so on. Use the Label Numbers port to specify the objects in the label matrix for which the block calculates statistics. The input to this port must be a vector of scalar values that correspond to the labeled regions in the label matrix.
For rectangular ROIs, use the ROI portion to process parameter to specify whether to calculate the statistical value for the entire ROI or just the ROI perimeter. For more information about the format of the input to the ROI port when you set the ROI to a rectangle or a line, see the Draw Shapes block reference page.
Output = Individual statistics for each ROI
Flag Port Output  Description 

0  ROI is completely outside the input image. 
1  ROI is completely or partially inside the input image. 
Output = Single statistic for all ROIs
Flag Port Output  Description 

0  All ROIs are completely outside the input image. 
1  At least one ROI is completely or partially inside the input image. 
If the ROI is partially outside the image, the block only computes the statistical values for the portion of the ROI that is within the image.
Output = Individual statistics for each ROI
Flag Port Output  Description 

0  Label number is not in the label matrix. 
1  Label number is in the label matrix. 
Output = Single statistic for all ROIs
Flag Port Output  Description 

0  None of the label numbers are in the label matrix. 
1  At least one of the label numbers is in the label matrix. 
The parameters on the Data Types pane of the block dialog are only used for complex fixedpoint inputs. The sum of the squares of the real and imaginary parts of such an input are formed before a comparison is made, as described in Value Mode. The results of the squares of the real and imaginary parts are placed into the product output data type. The result of the sum of the squares is placed into the accumulator data type. These parameters are ignored for other types of inputs.
The Main pane of the Maximum block dialog appears as follows.
Specify the block's mode of operation:
Value and Index — Output both the value and the index location.
Value — Output the maximum value of each input matrix. For more information, see Value Mode.
Index— Output the onebased index location of the maximum value. For more information, see Index Mode.
Running — Track the maximum value of the input sequence over time. For more information, see Running Mode.
For the Value, Index, and Value and Index modes, the 2D Maximum block produces identical results as the MATLAB^{®} max function when it is called as [y I] = max(u,[],D), where u and y are the input and output, respectively, D is the dimension, and I is the index.
Specify whether the block should find the maximum of the entire input each row, each column, or dimensions specified by the Dimension parameter.
Specify the reset event that causes the block to reset the running maximum. The rate of the reset signal must be a positive integer multiple of the rate of the data signal input. This parameter appears only when you set the Mode parameter to Running. For information about the possible values of this parameter, see Resetting the Running Maximum.
Specify the dimension (onebased value) of the input signal, over which the maximum is computed. The value of this parameter cannot exceed the number of dimensions in the input signal. This parameter applies only when you set the Find the maximum value over parameter to Specified dimension.
Select this check box to calculate the statistical value within a particular region of each image. This parameter applies only when you set the Find the maximum value over parameter to Entire input, and the block is not in running mode.
Specify the type of ROI you want to use. Your choices are Rectangles, Lines, Label matrix, or Binary mask.
When you set this parameter to Rectangles or Lines, the Output flag indicating if ROI is within image bounds check box appears in the dialog box. If you select this check box, the Flag port appears on the block.
When you set this parameter to Label matrix, the Label and Label Numbers ports appear on the block and the Output flag indicating if input label numbers are valid check box appears in the dialog box. If you select this check box, the Flag port appears on the block.
See ROI Output Statistics for details.
Specify whether you want to calculate the statistical value for the entire ROI or just the ROI perimeter. This parameter applies only when you set the ROI type parameter to Rectangles.
Specify the block output. The block can output a vector of separate statistical values for each ROI or a scalar value that represents the statistical value for all the specified ROIs. This parameter does not apply when you set the ROI type parameter, to Binary mask.
When you select this check box, the Flag port appears on the block. This check box applies only when you set the ROI type parameter to Rectangles or Lines. For a description of the Flag port output, see the tables in ROI Processing.
When you select this check box, the Flag port appears on the block. This check box applies only when you set the ROI type parameter to Label matrix. For a description of the Flag port output, see the tables in ROI Processing.
The Data Types pane of the Maximum block dialog appears as follows.
Note: The parameters on the Data Types pane are only used for complex fixedpoint inputs. The sum of the squares of the real and imaginary parts of such an input are formed before a comparison is made, as described in Value Mode. The results of the squares of the real and imaginary parts are placed into the product output data type. The result of the sum of the squares is placed into the accumulator data type. These parameters are ignored for other types of inputs. 
Select the Rounding Modes for fixedpoint operations.
Select the Overflow mode for fixedpoint operations.
Specify the product output data type. See FixedPoint Data Types and Multiplication Data Types for illustrations depicting the use of the product output data type in this block. You can set it to:
A rule that inherits a data type, for example, Inherit: Same as input
An expression that evaluates to a valid data type, for example, fixdt([],16,0)
Click the Show data type assistant button to display the Data Type Assistant, which helps you set the Product output data type parameter.
See Specify Data Types Using Data Type Assistant for more information.
Specify the accumulator data type. See FixedPoint Data Types for illustrations depicting the use of the accumulator data type in this block. You can set this parameter to:
A rule that inherits a data type, for example, Inherit: Same as product output
An expression that evaluates to a valid data type, for example, fixdt([],16,0)
Click the Show data type assistant button to display the Data Type Assistant, which helps you set the Accumulator data type parameter.
See Specify Data Types Using Data Type Assistant for more information.
Select this parameter to prevent the fixedpoint tools from overriding the data types you specify on the block mask.
The ex_vision_2dmaximumex_vision_2dmaximum example finds the maximum value within two ROIs. The model outputs the maximum values and their onebased [x y] coordinate locations.
2D Mean  Computer Vision System Toolbox 
2D Minimum  Computer Vision System Toolbox 
MinMax  Simulink 
max  MATLAB 