Data 'gestureType': Character outputs are not supported in Simulink and Stateflow. Cast 'gestureType' to int8 or uint8 instead.

I am a new user in MATLAB. I can not find the solution. Please help me how to solve this!

[Fangjun Jiang]

What release of MATLAB?

[Tanzil Haq]

MATLAB 2021b

Answer 1

[Fangjun Jiang]

MATLAB Function block does not support 'char' data type, so you can't write y='abc' for example.

But since R2019b, it supports 'string' data type, so you can write y="abc".

Most likely, making the above change should resolve the problem.

https://www.mathworks.com/help/simulink/slref/matlabfunction.html

[Walter Roberson]

https://www.mathworks.com/help/simulink/ug/data-types-supported-by-simulink.html lists the supported built-in signal data types (there is also support for fixed-point numbers). As @Fangjun Jiang indicates, string() is supported by not char

[Walter Roberson]

Your function is currently define along the lines of

[gestureType, gestureThreshold, gestureSensitify] = fcn(something or other)

and currently has lines as

if something
    gestureType = 'open';
elseif somethingelse
    gestureType = 'back';
elseif somethirdting
    gestureType = 'cancel';
else
    gestureType = 'unknown';
end

Possibly you have arranged so that all of the character vectors are the same length, possibly not.

This code will not work because it is not possible to pass character vectors as simulink signals.

With new enough (R2019b and newer) MATLAB, you can convert to

if something
    gestureType = "open";
elseif somethingelse
    gestureType = "back";
elseif somethirdting
    gestureType = "cancel";
else
    gestureType = "unknown";
end

and that would work because Simulink now supports string signals -- but still not character vectors.

If you were using an older Simulink, you would need to instead use something like

if something
    gestureType = Sig8('open');
elseif somethingelse
    gestureType = Sig8('back');
elseif somethirdting
    gestureType = Sig8('cancel');
else
    gestureType = Sig8('unknown');
end

along with an auxillary function,

function out = Sig8(in)
   %build a uint8 signal from a variable-length character vector
   %numeric signals that are variable length are harder to deal with
   %so we blank pad and take only the first 8 characters of the result.
   %If you need more than 8 characters downstream, adjust the 8 here.
   N = 8;
   temp1 = [in, blanks(N)];
   temp2 = temp1(1:N);
   out = uint8(temp2);
end

after which gestureType would be a 1 x 8 vector of uint8 . Then, if some next step needed the gesture in character form it would use

gT = deblank(char(gestureType));

[Tanzil Haq]

function [gestureType, gestureThreshold, gestureSensitivity] = interpretGesture(data, threshold, sensitivity)
% Initialize output variables
gestureType = '';  % Default empty gesture type
gestureThreshold = threshold;  % Pass through the provided threshold
gestureSensitivity = sensitivity;  % Pass through the provided sensitivity

% Assuming the data input is a concatenated matrix with values for Up, Down, Left, and Right directions
upData = data(1);
downData = data(2);
leftData = data(3);
rightData = data(4);

% Logic to interpret gestures based on the sensor data for each direction
gestureTypes = {'Up', 'Down', 'Left', 'Right'};
gestureData = [upData, downData, leftData, rightData];

[~, maxIdx] = max(gestureData); % Finding the index with the maximum value

% Check if the maximum value exceeds threshold + sensitivity for that direction
if gestureData(maxIdx) > (threshold + sensitivity)
    gestureType = gestureTypes{maxIdx}; % Get the corresponding gesture type
else
    gestureType = 'No Gesture';
end
end

I used this code but it is not working can you please help me to make a correction on it or modify it? My project is gesture based home automation and in simulink i am trying hard to do the simulation part which i can not do due to the problem i am facing in this code.

[Walter Roberson]

As you are using R2019b or later you can use string signals.

function [gestureType, gestureThreshold, gestureSensitivity] = interpretGesture(data, threshold, sensitivity)
    % Initialize output variables
    gestureType = "";  % Default empty gesture type
    gestureThreshold = threshold;  % Pass through the provided threshold
    gestureSensitivity = sensitivity;  % Pass through the provided sensitivity
    
    % Assuming the data input is a concatenated matrix with values for Up, Down, Left, and Right directions
    upData = data(1);
    downData = data(2);
    leftData = data(3);
    rightData = data(4);
    
    % Logic to interpret gestures based on the sensor data for each direction
    gestureTypes = ["Up", "Down", "Left", "Right"];
    gestureData = [upData, downData, leftData, rightData];
    
    [~, maxIdx] = max(gestureData); % Finding the index with the maximum value
    
    % Check if the maximum value exceeds threshold + sensitivity for that direction
    if gestureData(maxIdx) > (threshold + sensitivity)
        gestureType = gestureTypes(maxIdx); % Get the corresponding gesture type
    else
        gestureType = "No Gesture";
    end
end

... but have you considered that it might be easier to pass around codes indicating which gesture it was? Perhaps even an enumeration? https://www.mathworks.com/help/simulink/ug/about-simulink-enumerations.html

[Fangjun Jiang]

It might not matter but change the first line to be

gestureType = "No Gesture" or gestureType = ""

[Walter Roberson]

Good point, @Fangjun Jiang, I made that edit.