MATLAB: Error : Indices must either be real positive integers or logicals.

We take a look at this line first

X(:,iel) = coordinates(nodes(iel,:),1) ;

put display(iel) infront of this line

display(iel)  
X(:,iel) = coordinates(nodes(iel,:),1) ;

iel is indeces, it must be real positive integers or logical. Therefore, 0, negative value, floating value are not allowed.

Best Answer

I think your error is from here

nodes(iel,:)

first you assign zero to nodes with 400 x 8 dimension

nodes = zeros(nel,nnel) ;

later in your reshape you assign dimension 21*21 to NodeNo

NodeNo = reshape(NodeNo,npx,npy);

Then reshape nodes follow below

nodes(:,1) = reshape(NodeNo(1:npx-1,1:npy-1),nel,1);

that's mean now nodes(:,1) has dimesion 441 * 1 then you do similar thing to nodes(:,2), nodes(:,3), nodes(:,4).

Now, Try to think, what is the dimension of nodes(:,5)? originally, you assign zero to nodes(:,5) from 1 to 400, then with new expansion of your nodes, 401 to 441 will be NaN.

At the end

X(:,iel) = coordinates(NaN,1) ;

So how to solve it ? I guess simply to change this line to 21*21 dimension

nodes = zeros(npx,npy) ;

% your npx is 21 dimension, npy is also 21 dimension

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MATLAB: Error: Error while evaluating UIControl Callback.

You specified the callback as a character vector. Callbacks that are character vectors, are executed in the base workspace, and so only have access to variables defined in the base workspace.

The seemingly obvious change would be to

ShowElements = uicontrol('style','toggle','string','Elements','value',0,.... 'position',[pos(1) pos(2) pos(3) pos(4)],'background','white','callback',.... @(varargin) SHOWELEMENTS(ShowElements,ShowNodes,coordinates,X,Y,nel,nodes,nnode));

But that will not work. When you create an anonymous function, the value of the mentioned variables are captured as of the time of the call, and at that time, ShowElements has not yet been defined.

What would work though is

 ShowElements = uicontrol('style','toggle','string','Elements','value',0,.... 'position',[pos(1) pos(2) pos(3) pos(4)],'background','white','callback',.... @(hObject,event) SHOWELEMENTS(hObject,ShowNodes,coordinates,X,Y,nel,nodes,nnode)');

The corresponding change will not work for the earlier ShowNodes, because the callback for it refers to ShowElements that would not have been defined yet.

The approach that will work for both is to create both the uicontrol without putting in the callbacks, so that the handles both get defined. Then you can set the Callback properties of the two to @(varargin) followed by the existing callback without the surrounding quote marks.

MATLAB: How can i connect the ‘.’ points of the given figure. i don’t want to connect ‘*’ with any point

Try using the following code to plot:

%% Plot
lw = 2; % LineWidth
ms = 15; % MarkerSize
figure
xlim([-0.2 1.2])
ylim([-0.2 1.2])
hold on
for i = 1:Nx
    plot([x1(i) x4(end-Nx+i)],[y1(i) y4(end-Nx+i)],'k-','LineWidth',lw);
end
plot([x2(Nx) x3(end)],[y2(Nx) y3(end)],'k-','LineWidth',lw);
for i = 1:Ny
    plot([x1(Nx*(i-1)+1) x2(i*Nx)],[y1(Nx*(i-1)+1) y2(i*Nx)],'k-','LineWidth',lw);
end
plot([x4(Nx*(Ny-1)+1) x3(end)],[y4(Nx*(Ny-1)+1) y3(end)],'k-','LineWidth',lw);
plot(x1,y1,'b.','MarkerSize',ms)
plot(x2,y2,'b.','MarkerSize',ms)
plot(x3,y3,'b.','MarkerSize',ms)
plot(x4,y4,'b.','MarkerSize',ms)
plot(x5,y5,'b.','MarkerSize',ms)
plot(x6,y6,'b.','MarkerSize',ms)
plot(x7,y7,'b.','MarkerSize',ms)
plot(x8,y8,'b.','MarkerSize',ms)
plot(x9,y9,'b*','MarkerSize',ms)
hold off

The expected output for Nx=3 and Ny=3 is:

If you want to display a grid, it will dpend on the XTick and YTick values. Have a look at those properties at: https://www.mathworks.com/help/matlab/ref/matlab.graphics.axis.axes-properties.html#budumk7-XTick

Best Answer

Related Solutions

MATLAB: Error: Error while evaluating UIControl Callback.

MATLAB: How can i connect the ‘.’ points of the given figure. i don’t want to connect ‘*’ with any point

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