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Basic: calling a function

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Stina Ravdna Lorås
评论： Stina Ravdna Lorås 2021-1-25
I have a probably very basic question:
I have made a function file in matlab and want to call it within my script file. The script is not finished, so I just need to consentrate to get the function "central_difference" working for now. I get an error message saying that the variable 'greyimg' is not defined when I call central_difference. I don´t understand why, since it is defined....? And when the function works, should it not also be able to plot the subplots 152-154
Code here:
Script file:
clc;
clear all;
gridimg = im2double(imread('grid.jpg'));
grayimg = rgb2gray(gridimg);
[Ix,Iy,Im] = central_difference(greyimg);
[x,y,theta] = extract_edges(Ix, Iy, Im, edge_threshold);
figure(6);
set(gcf,'Position',[100 100 1000 300])
subplot(151); imshow(img_blur); xlim([300, 500]); title('Blurred input');
subplot(152); imshow(Ix, [-0.05, 0.05]); xlim([300, 500]); title('Gradient in x');
subplot(153); imshow(Iy, [-0.05, 0.05]); xlim([300, 500]); title('Gradient in y');
subplot(154); imshow(Im, [ 0.00, 0.05]); xlim([300, 500]); title('Gradient magnitude');
Function file:
function [Ix, Iy, Im] = central_difference(Img)
Ix = zeros(size(Img)); % Placeholder
Iy = zeros(size(Img)); % Placeholder
Im = zeros(size(Img)); % Placeholder
kernel = [1/2 0 -1/2];
for i=1: size(Img, 1) %alle rader i grayimg
Ix(i, :) = conv(Img(i,:), kernel, "same"); %conv med kernel
end
for j=1: size(Img, 2) %alle kolonner i grayimg
Iy(:, j) = conv(Img(:,j), kernel, "same");
end
Im = sqrt(Ix.^2 + Iy.^2);
end

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采纳的回答

Cris LaPierre
Cris LaPierre 2021-1-25
编辑：Cris LaPierre 2021-1-25
The error is telling you that greyimg does not exist. When you create the variable, you call it grayimg (with an a instead of e)
grayimg = rgb2gray(gridimg);
^ % gray
[Ix,Iy,Im] = central_difference(greyimg);
^ % grey
  1 个评论
Stina Ravdna Lorås
Stina Ravdna Lorås 2021-1-25
And so basic could it actually be :D
Obviously too tired. Thought I had misunderstod the consept of functions. Thank you!

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