How can i convert the first image(Red) like the second one(Black)?

[Rik]

You want to fit a certain function to your data. What have you tried so far?

[siet ece]

cover=imread('Lenna.png');
coverplane1=int32(cover(:,:,1));

for i=1:512
    for j=1:511
        PixelDiffOriginal(i,1:511)=coverplane1(i,j)-coverplane1(i,j+1);
    end
end

[N1,edges1]=histcounts(PixelDiffOriginal);
edges1=edges1(2:end)-(edges1(2)-edges1(1))/2;
plot(edges1,N1);

%% i just tried to plot a graph(black graph) but i got the red graph, how can i obtain the black graph? 

Answer 1

[Image Analyst]

Use plot() instead of stem().

[siet ece]

i used plot command only

[Image Analyst]

How did you plot the red? Why does the red curves go down to 0? Are there zeros in the data that you don't want to plot? You can just delete the zeros and plot that:

nonZeroIndexes = occurrences > 0;
plot(pixelDifferences(nonZeroIndexes), occurrences(nonZeroIndexes), 'k-', 'LineWidth', 2);

[siet ece]

Thank u so much, your code works, but i cant get a smooth cure like the above one. is that possible to make this curve smooth like the above one(black cure)

[Image Analyst]

The black curve in your original post doesn't look smooth to me. But anyway, you can smooth the data and then plot the smoothed data with a sliding polynomial fit filter, sgolayfilt() in the Signal Processing Toolbox.

polynomialOrder = 2; % Larger for less smoothing.
windowWidth = 7; % Larger for more smoothing.
smoothedSignal = sgolayfilt(signal, polynomialOrder, windowWidth);
plot(smoothedSignal, 'b-', 'LineWidth', 3);
grid on;
title('Smoothed Signal', 'FontSize', 20);

If you don't have sgolayfilt(), try movmean().

[siet ece]

its working, thank u so much.