Error: Edge function: variable might be used before it is defined

Hi,

I want to use the edge function and I keep getting an error if I use it inside a function.

Unrecognized function or variable 'edge'.

Error in detectEdge (line 6)

bscan = edge(bscan, 'Canny', canny_threshold);

Error in BugFixingFunctions (line 32)

img = detectEdge(img);

Here is my Code:

function [bscanout] = detectEdge(bscan)
    % segment edge
    canny_threshold = [0.1, 0.2]; % Anpassen der Schwellenwerte für die Kantenextraktion
    bscan = edge(bscan, 'Canny', canny_threshold);
    [rows, columns] = size(bscan);

    % delete Isle
    bscan = bwareaopen(bscan, 150);

    temp = zeros(rows,columns);
    for i = 1:columns
        for j = 1:rows
            if bscan(j,i) == 1
                temp(j,i) = 1;
                break;
            end
        end
    end
    temp(350:end,:) = 0;
    temp(1:100,:) = 0;

    % Interpolate edge Without high peaks
    bscanout = temp;
    [yValues, xValues] = find(temp);
    clear temp;

    %if gap is at the start
    if xValues(1) ~= 1 && xValues(1) ~= 2
        xValues = [1; 2; xValues];
        yValues = [yValues(end-4); yValues(end-4); yValues];
    elseif xValues(1) ~= 1 && xValues(1) == 2
        xValues = [1; xValues];
        yValues = [yValues(end-4); yValues];
    end

    %if gap is at the end
    if xValues(end) ~= columns && xValues(end) ~= columns -1
        xValues = [xValues; columns - 1; columns];
        yValues = [yValues; yValues(3); yValues(3)];
    elseif xValues(end) ~= columns && xValues(end) == columns -1
        xValues = [xValues; columns];
        yValues = [yValues; yValues(3)];
    end

    %interpolate edge for the missing gap
    for i = 1:length(xValues) - 1
        if xValues(i) + 1 ~= xValues(i + 1)
            edge = interp1(xValues(i-1:i + 1),yValues(i-1:i + 1),1:columns,"pchip");
            edge = round(edge);
            for j = xValues(i):xValues(i+1)
                bscanout(edge(j),j) = 1;
            end
        end
    end
end

If I use the edge function outside the function I wrote, I dont get this error

Answer 1

[DGM]

I'm pretty sure the reason that's happening is because later on in the same scope, you're shadowing the function by creating a variable with the same name. The linter assumes that edge is supposed to be a variable, when you're treating it as both. Avoid creating variables that have the same name as functions. If you rename your edge variable, the warning should go away.

[Kjell]

thank you

Answer 2

[Image Analyst]

Try this:

edgeData = interp1(xValues(i-1:i + 1),yValues(i-1:i + 1),1:columns,"pchip");
edgeData = round(edgeData);
for j = xValues(i):xValues(i+1)
    bscanout(edgeData(j),j) = 1;
end

[Kjell]

thank you