I'm getting Index in position 2 exceeds array bounds error

clc
clear all
close all

%% Input arguments

rec=load('data.mat');
received=cell2mat(struct2cell(rec));


x_meas=0:0.1:9.9;  
temp=0:0.1:9.9;
theta_meas=atan(10./temp);
temp1=0:1:99;
beam_angle=atan(10./temp1);

Fs=60;             
x_min=1;            
x_max=10;         
y_min=1;            
y_max=10;           

r_begin=0.4;        % The range that corresponds to the first sample of the data
resolution=1;       % Spatial resolution of the image in meters

% Initialization
c=0.2999;   % Speed of light

% Information on the distances corresponding to samples
sample_spacing =c/Fs/2;     % The distance between two samples .

x_size = floor((x_max-x_min)/resolution);   % Number of pixels in the x- direction
y_size = floor((y_max-y_min)/resolution);   % Number of pixels in the y- direction

% Initialize matrices
result=zeros(x_size,y_size);    % Final Image Result
range_signal=result;    % Matrix that describes which pixels are visible for the antenna
% Vectors with the x- and y- coordinates that correspond to the samples
x_pixel=linspace(x_min,x_max,x_size);
y_pixel=linspace(y_min,y_max,y_size);
% Min & max angles bepalen
theta_min=theta_meas-beam_angle;    % Angle at which the beam starts with respect to horizontal
theta_max=wrapToPi(theta_meas+beam_angle);  % Angle at which the beam ends with respect to horizontal

for i =1:length(x_meas)     % Loop over the measurements
    
    % Reset temporary matrix
    range_signal=ones(x_size,y_size);
    
    % Determine for a certain height , at which x- value the beam starts and determine which pixels are then not visible by the antenna before the beam .
    if (theta_min(i)>0)
        for j=1:y_size
            x_theta_min=y_pixel(j)/tan(theta_min(i))+x_meas(i);
            x_theta_min=min([x_theta_min,x_max]);
            
            range_signal(:,j)=range_signal(:,j).*(x_pixel<= x_theta_min)';
        end
    end
    
    % Determine for a certain height , at which x- value the beam ends and determine which pixels are then not visible by the antenna after the beam .
    if (theta_max(i)>0)
        for j =1: y_size
            x_theta_max=y_pixel(j)/tan(theta_max(i))+x_meas(i);
            x_theta_max=max([ x_theta_max,x_min]);
            
            range_signal(:,j)=range_signal(:,j).*(x_pixel>=x_theta_max)';
        end
    end
    
    % For all the pixels that are visible for the antenna
    for xx=1:x_size
        for yy=1:y_size
            if range_signal(xx,yy) % ~= 0
                
                % Calculate the distance between measurement position and pixel
                distance_from_measurement=sqrt((x_pixel(xx)-x_meas(i))^2+y_pixel(yy)^2);
                
                % Find the corresponding signal value with the help of interpolation and add this to the result
                
                sample_actual=((distance_from_measurement-r_begin)/sample_spacing );
                
                sample_actual_floor=max([floor(sample_actual),1]);
                
                sample_actual_mod=mod(sample_actual,1);
                
                result(xx,yy)=result(xx,yy)+(1-sample_actual_mod)*received(i,sample_actual_floor) +...
                    sample_actual_mod*received(i,(sample_actual_floor+1));
                
            end
        end
    end
end

result

im getting the error in this line given below

result(xx,yy)=result(xx,yy)+(1-sample_actual_mod)*received(i,sample_actual_floor) +...
                    sample_actual_mod*received(i,(sample_actual_floor+1));

error is like this

Index in position 2 exceeds array bounds (must not exceed 4096).

Error in BPA (line 87)

(1-sample_actual_mod)*received(i,sample_actual_floor) +...

.. please help me

[KSSV]

What is received?

[Sowjanya Lanka]

I have taken like the below.. it is a 100x4096 data

rec=load('data.mat');

received=cell2mat(struct2cell(rec));

[Image Analyst]

What is the error? There is no bold line. Please give us ALL THE RED TEXT after you read this:

TUTORIAL: How to ask a question (on Answers) and get a fast answer

Once you know how to debug you'll know what the variable in second index is, and what its value is. This will help:

Debugging in MATLAB | Doug's MATLAB Video Tutorials

[Jan]

"in that bold line im getting the error" - there is no bold face in formatted code.

[Sowjanya Lanka]

sir i just modified my code please check once..

[Sowjanya Lanka]

I've done debugging the code in R2018a. It works for a few loops and after that the second index position data goes beyond 4096.. im unable to resolve it

Answer 1

[sanidhyak]

Hi Sowjanya,

I too faced the same error when I replicated your code and ran it locally.

The error message: “Index in position 2 exceeds array bounds (must not exceed 4096).” indicates that “sample_actual_floor + 1” is exceeding the bounds of the “received” matrix. To fix this, it should be ensured that “sample_actual_floor + 1” does not exceed the number of columns in “received”.

Kindly refer to the following corrected part of the code:

for yy=1:y_size 
    if range_signal(xx,yy) % ~= 0 
        
        % Calculate the distance between measurement position and pixel 
        distance_from_measurement=sqrt((x_pixel(xx)-x_meas(i))^2+y_pixel(yy)^2); 
        
        % Find the corresponding signal value with the help of interpolation and add this to the result 
        
        % Ensure sample_actual_floor does not exceed the last index 
        max_samples = size(received, 2); % Get the number of columns (samples) 
        
        sample_actual = (distance_from_measurement - r_begin) / sample_spacing; 
        sample_actual_floor = max(1, min(floor(sample_actual), max_samples - 1)); % Ensure within bounds 
        sample_actual_mod = mod(sample_actual, 1); % Get the fractional part 
        
        % Interpolate signal value safely 
        result(xx,yy) = result(xx,yy) + ... 
            (1 - sample_actual_mod) * received(i, sample_actual_floor) + ... 
            sample_actual_mod * received(i, sample_actual_floor + 1); 
    end 
end 

Here, “max_samples = size(received, 2)” gets the total number of values. “sample_actual_floor = max(1, min(floor(sample_actual), max_samples - 1))” keeps it within a safe range so that “sample_actual_floor + 1” does not go out of limits. This would prevent the error and would also ensure proper calculation.

Cheers & Happy Coding!