indexing must appear last in an index espression

Question

Bhargavkrishna Kondreddy 2016-10-24

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https://ww2.mathworks.cn/matlabcentral/answers/308968-indexing-must-appear-last-in-an-index-espression

编辑： Jan 2016-10-26

采纳的回答： Jan

Xsum =A(1)(:,3); error is at this point for k = 2:299 Xsum=Xsum+A(k)(:,3); end

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Answer 1

Jan 2016-10-25

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https://ww2.mathworks.cn/matlabcentral/answers/308968-indexing-must-appear-last-in-an-index-espression#answer_240505

编辑：Jan 2016-10-26

在 MATLAB Online 中打开

A(k) is the k.th element of the array A. Then indexing another time by "(:,3)" is not valid Matlab syntax. We cannot guess the purpose of this code, so please explain the class and dimensions of A and what you want to achieve.

[EDITED, after you provided the code]

I guess that:

Xsum = A(1)(:,3)

should be

Xsum =A{1}(:,3)

and the same for "Xsum=Xsum+A(k)(:,3)".

Compare it with the lines:

Ysum = A{1}(:,4); for m = 2:299 Ysum=Ysum+A{m}(:,4); end

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Answer 2

Bhargavkrishna Kondreddy 2016-10-25

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https://ww2.mathworks.cn/matlabcentral/answers/308968-indexing-must-appear-last-in-an-index-espression#answer_240525

this code is meant for importing 300 .txt files and summing and mean of all values of the files and plotting the final results. clear all clc;

% Generating 2D Meshgrid [X,Y] = meshgrid(185:8:849,169:8:625); %-------------------------------

% Importing all the 300 files

files = dir( 'imageset1_*.txt'); for i=1:numel(files) A{i} = dlmread( files(i).piv, '\t', 3 , 0 ); end

% Summation of X-components of the 300 files

Xsum =A(1)(:,3); for k = 2:299 Xsum=Xsum+A(k)(:,3); end

% Taking average of the X-components of the 300 files

Xavg = Xsum/299; %Xavg(isnan(Xavg)) = 0;

% Summation of Y-components of the 300 files

Ysum = A{1}(:,4); for m = 2:299 Ysum=Ysum+A{m}(:,4); end

%Taking average of the Y-components of the 300 files

Yavg = Ysum/299; %Yavg(isnan(Yavg)) = 0;

% Calculating the magnitude of the X-component and Y-component

Zavg = sqrt(Xavg.^2+Yavg.^2);

% Making the NaN Values Zero

Zavg(isnan(Zavg)) = 0;

% Creating a Dummy Matrix of 12 x 18

Zplot = rand(58,84); %--------------------------------------------------

% Assigning the Value of Zavg in the Dummy Matrix

for e = 1:4872 %------------------------------------------------------- Zplot(e)=Zavg(e); end

%*********************************************************************** % Creating a Dummy Matrix of 12 x 18

Xplot = rand(58,84); %--------------------------------------------------

% Assigning the Value of Zavg in the Dummy Matrix

for e = 1:4872 %------------------------------------------------------- Xplot(e)=Xavg(e); end

% Creating a Dummy Matrix of 12 x 18

Yplot = rand(58,84); %--------------------------------------------------

% Assigning the Value of Zavg in the Dummy Matrix

for e = 1:4872 %------------------------------------------------------- Yplot(e)=Yavg(e); end

%***********************************************************************

%Contour Plot figure; contour(X,Y,Zplot,100,'LineWidth',3,'Fill','on','clipping','off'); xlabel('\fontsize{20}X - Pixels'); ylabel('\fontsize{20}Y - Pixels'); title('\fontsize{22}CONTOUR PLOT'); colorbar; hold on; quiver(A{1}(:,1),A{1}(:,2),Xavg,Yavg,'color','black'); axis([200 800 100 700]);%%%%%%%%%%%%%% colormap('jet');

% Setting the minimum and the maximum limit of the colormap and colorbar on the contour plot caxis([0 10]);

% Overlapping the overlapped images with the velocity vectors

figure; load('matlab.mat'); imcropped_93=imcrop(imcell1_93,[195 182 631 434]); imshow(imcropped_93); hold on; quiver(A{1}(:,1)-195,A{1}(:,2)-182,Xavg,Yavg,'color','yellow');

hold on;