Index in position 1 exceeds array bounds.

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Matis Tartie 2022-6-3

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1732900-index-in-position-1-exceeds-array-bounds

回答： Matis Tartie 2022-6-3

As a task I have to implement a RANSAC algorithm. There is an array called correspondences which is 4xn, where the first 2 rows are x1 and y1 and the last two rows are x2 and y2. These are coordinates for pixels. The task here is to seperate the coordinates into their own homogenious variables. Before that one must provide some optional variables for the function. I used an Input Parser for that and it seems to work. This is what I did:

function [epsilon, p, tolerance, x1_pixel, x2_pixel] = F_ransac(correspondences, varargin)

% This function implements the RANSAC algorithm to determine

% robust corresponding image points

p1 = inputParser;

addOptional(p1, 'epsilon', 0.5, @(x)validateattributes(x, {'numeric'}, {'<',1}, {'>',0}));

addOptional(p1, 'p', 0.5, @(x)validateattributes(x, {'numeric'}, {'<',1}, {'>',0}));

addOptional(p1, 'tolerance', 0.01, @(x)validateattributes(x, {'numeric'}));

parse(p1);

epsilon = p1.Results.epsilon;

p = p1.Results.p;

tolerance = p1.Results.tolerance;

x1_pixel = ones(3,size(correspondences,2));

x1_pixel(1:2,:) = correspondences(1:2,:);

x2_pixel = ones(3,size(correspondences,2));

x2_pixel(1:2,:) = correspondences(3:4,:);

end

This is constantly giving me the error:

Index in position 1 exceeds array bounds.

Error in F_ransac (line 16)

x1_pixel(1:2,:) = correspondences(1:2,:);

Why is it giving me this error? What could I do to avoid it?

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VBBV 2022-6-3

在 MATLAB Online 中打开

correspondences = rand(3,5); % less than 4 
F_ransac(correspondences,3)
Index in position 1 exceeds array bounds. Index must not exceed 3.

Error in solution>F_ransac (line 19)
    x2_pixel(1:2,:) = correspondences(3:4,:);
function [epsilon, p, tolerance, x1_pixel, x2_pixel] = F_ransac(correspondences, varargin)
    % This function implements the RANSAC algorithm to determine 
    % robust corresponding image points
    
    p1 = inputParser;
    addOptional(p1, 'epsilon', 0.5, @(x)validateattributes(x, {'numeric'}, {'<',1}, {'>',0}));
    addOptional(p1, 'p', 0.5, @(x)validateattributes(x, {'numeric'}, {'<',1}, {'>',0}));
    addOptional(p1, 'tolerance', 0.01, @(x)validateattributes(x, {'numeric'}));
    parse(p1);
    epsilon = p1.Results.epsilon;
    p = p1.Results.p;
    tolerance = p1.Results.tolerance;
    x1_pixel = ones(3,size(correspondences,2));
    x1_pixel(1:2,:) = correspondences(1:2,:);
    x2_pixel = ones(3,size(correspondences,2));
    x2_pixel(1:2,:) = correspondences(3:4,:);
end 

May be you are calling function with input arguments of incorrect size

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Answer 1

Chunru 2022-6-3

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1732900-index-in-position-1-exceeds-array-bounds#answer_977510

在 MATLAB Online 中打开

It seems that your code works well. Can you show how the error occurs?

x = randn(4, 5)
x = 4×5
    1.7007    1.0577    1.2506    0.4107    1.0085
   -0.3642    0.0145    0.4001   -0.3132    0.0327
    0.0062   -0.1212    0.1764   -1.7733   -1.0230
   -0.3822   -0.4836    0.4640   -0.9320   -1.5065
F_ransac(x)
ans = 0.5000
function [epsilon, p, tolerance, x1_pixel, x2_pixel] = F_ransac(correspondences, varargin)
    % This function implements the RANSAC algorithm to determine 
    % robust corresponding image points
    
    p1 = inputParser;
    addOptional(p1, 'epsilon', 0.5, @(x)validateattributes(x, {'numeric'}, {'<',1}, {'>',0}));
    addOptional(p1, 'p', 0.5, @(x)validateattributes(x, {'numeric'}, {'<',1}, {'>',0}));
    addOptional(p1, 'tolerance', 0.01, @(x)validateattributes(x, {'numeric'}));
    parse(p1);
    epsilon = p1.Results.epsilon;
    p = p1.Results.p;
    tolerance = p1.Results.tolerance;
    x1_pixel = ones(3,size(correspondences,2));
    x1_pixel(1:2,:) = correspondences(1:2,:);
    x2_pixel = ones(3,size(correspondences,2));
    x2_pixel(1:2,:) = correspondences(3:4,:);
end 