getting errors in running this.

dmp = M.data.damping;

c=damp(:,:);

Dot indexing is not supported for variables of this type.

Error in Untitled (line 13)

dmp = M.data.damping; %% damping matrix of the structure

[Guillaume]

Your code expect M or M.data to be something that can be indexed with ., possibly a structure. The error message tells you it isn't.

The problem is earlier in your code, wherever M or M.data is created.

[Chaudhary P Patel]

%%% this is my code initiation part%%%%%%%%%

inpf=input('File name of input file data   ','s');
M=importdata([inpf,'.xlsx']);
%Table of nodes and coordinates of column
nod=M.data.Node;
nj=max(nod(:,1));% No. of joints or nodes
%Table of elments of column core and beam
elem=M.data.Element;  %Elelment data for Column
ne=max(elem(:,1)); %No. of elements
stif=M.data.Stiffness; %% stiffness matrix of the structure
K=stif(:,:);
mas=M.data.Mass;  % mass matrix of the structure
M=mas(:,:); 
dmp = M.data.damping; %%  damping matrix of the structure
C=dmp(:,:);

Answer 1

[Guillaume]

I would recommend you use readtable instead of importdata. importdata may not return what you expected if the file format change. However, it is not the problem here.

M.data is indeed a structure ... until you stomp on it and replace it with a matrix:

M=mas(:,:);

From this point onward, you've replaced the original M so of course, M.data.damping no longer work.

Morale of the story: Use better variable names, ones that are not ambiguous, so you know what they actually contain. I would recommend using complete words with no abbreviation, e.g. importeddata instead of M, mass instead of the other M, stiffness, damping, etc.

Also note, that

X = Y(:, :);

when Y is a 2D matrix is just a more complicated and confusing way of writing:

X = Y;

[Chaudhary P Patel]

thank you so much sir!!!