How to solve the error "Index in position 2 exceeds array bounds."

Hi, I'm running a code and I keep getting this error

'Index in position 2 exceeds array bounds'

How do i fix it please, The corona virus has really restricted my movement

[Walter Roberson]

We would need to see your code. If it reads in files, we would need the files as well.

[Rita Akonobi]

The full error it shows is below

>> truss2D_optimization ('buckling_check_1.txt')

Index in position 2 exceeds array bounds.

Error in truss2D_readdata (line 102)

loadednodes=pload(:,1);

Error in truss2D_optimization (line 19)

[coorddofvar0,fixeddata] = truss2D_readdata(filename);

The main code is

%**********************************************************************
% Program for optimization of linear elastic 2D trusses
%
% HISTORY
% September 2017, :   Initial coding as "truss2D.m"
% October   2018, :   Changes to turn into truss
%                    optimization program
%***********************************************************************
function [] = truss2D_optimization(filename)
%
global fixeddata
global R
global U
%
hold off;
%
% Read problem data from input data file (including a design)
%
[coorddofvar0,fixeddata] = truss2D_readdata(filename);
% set number of design variables
nvar=length(coorddofvar0);
%
% Print objective function and constraint array for data file design
%
%...objective function
[objfunction] = truss2D_objfunction(coorddofvar0);
disp('-------------------------------------------------------------------')
disp('                      2D TRUSS OPTIMISER')
disp('-------------------------------------------------------------------')
disp('DATA FILE DESIGN:')
aa=['Objective function = ',num2str(objfunction)];
disp(aa);
%...constraint array value for data file design
[C,Ceq] = truss2D_nlcon(coorddofvar0);
disp('Inequality constraint array =');
disp(C);
%
%
% Perform optimisation
%
% Set bounds for population using data file prescriptions
%...lower bounds for variable nodal coordinates
lowerbound=fixeddata.lowerbound;
%...upper bound;
upperbound=fixeddata.upperbound;
% Set other parameters of function ga
A=[];b=[];Aeq=[];beq=[];
% Call optimisation function
coorddofvaropt = ga(@truss2D_objfunction,nvar,A,b,Aeq,beq,lowerbound,upperbound,@truss2D_nlcon);
%
% Print objective funstion and constraint array for optimal design
[objfunction] = truss2D_objfunction(coorddofvaropt);
disp('-------------------------------------------------------------------')
disp('OPTIMAL DESIGN:')
aa=['Objective function = ',num2str(objfunction)];
disp(aa);
%...constraint array
[C,Ceq] = truss2D_nlcon(coorddofvaropt);
disp('Inequality constraint array =');
disp(C);
disp('-------------------------------------------------------------------')
disp('-------------------------------------------------------------------')
%
%
%
% Plot data file design and optimal design
%
amplfact=fixeddata.amplfact;
coorddoffix=fixeddata.coorddoffix;
dofcoordfix=fixeddata.dofcoordfix;
dofcoordvar=fixeddata.dofcoordvar;
F=fixeddata.F;
lnods=fixeddata.lnods;
ngdof=fixeddata.ngdof;
npoin=fixeddata.npoin;
% Arrange coordinates in usual 2-dimensional array format (node by node)
%...optimal design coordinates
coorddof(dofcoordfix)=coorddoffix;coorddof(dofcoordvar)=coorddofvaropt;
%...initial design coordinates
coorddof0(dofcoordfix)=coorddoffix;coorddof0(dofcoordvar)=coorddofvar0;
%...conversion to 2-dimensional arrays
coord=zeros(npoin,2);coord0=zeros(npoin,2);
for ipoin=1:npoin
    dofx=ipoin*2-1;dofy=ipoin*2;
    coord(ipoin,1)=coorddof(dofx);coord(ipoin,2)=coorddof(dofy);
    coord0(ipoin,1)=coorddof0(dofx);coord0(ipoin,2)=coorddof0(dofy);
end
%
truss2D_plotresult(amplfact,coord0,coord,F,lnods,ngdof,npoin,R,U)
% Clear all variables before terminating program
%
clear;
end
%%%%%%%%%%%%%%%%%%%%%%

Then it picks up data from this code

%**********************************************************************
% Reads all data for a 2D linear elastic truss
%
% HISTORY
% October   2018, :   Initial coding (from "truss2D.m")
%***********************************************************************
function [coorddofvar,fixeddata] = truss2D_readdata(filename)
%
% Set some basic variables
% ========================
% Number of degrees of freedom per node
ndofn=2;
% Number of nodes of the element
nnode=2;
%
% Read information from data file
% ===============================
%
fid = fopen(filename, 'r');

title = fscanf(fid, 'TITLE = %s',1);
%
% Total number of elements in the mesh
nelem = fscanf(fid, '\nELEMENTS = %d', 1);
%
% Table of connectivities
%
lnods = fscanf(fid, '\n%d %d %d %f %f', [nnode+3,nelem]);
lnods = lnods';sortrows(lnods,1);
%...cross-sectional areas
csarea = lnods(:,4);
%...second moment of areas
sndmoa = lnods(:,5);
%...store only connectivities in lnods
lnods = lnods(:,2:nnode+1);
%...create table of element global degrees of freedom
eldofX = lnods*ndofn-1; eldofY = lnods*ndofn;
eldofs = [ eldofX(:,1) eldofY(:,1) eldofX(:,2) eldofY(:,2) ];
%
% Nodal coordinates
%
npoin = fscanf(fid, '\nNODE_COORDINATES = %d', 1);
coord = fscanf(fid, '\n%d %f %f', [3, npoin]);
coord = coord';sortrows(coord,1);nodnumbers=coord(:,1);
coord = coord(:,2:3);
%...create table of nodal degrees of freedom
nodofs = [ nodnumbers*ndofn-1 nodnumbers*ndofn ];
%
%
% Prescribed displacements
%
nnodefix = fscanf(fid,'\nNODES_WITH_PRESCRIBED_DISPLACEMENTS = %d',1);
ipresc   = fscanf(fid, '\n%d %d %f %f', [2+ndofn, nnodefix]);
ipresc   = ipresc';fixednodes=ipresc(:,1);

%...create tables of fixed dofs and corresponding prescribed values
ifdoffix = zeros(npoin*ndofn,1); icount = 0;
for inodefix = 1:nnodefix
    ipoin=ipresc(inodefix,1);
    dofX=nodofs(ipoin,1);dofY=nodofs(ipoin,2);
    if  ipresc(inodefix,2)==11
        ifdoffix(dofX)=1;
        ifdoffix(dofY)=1; 
        icount = icount+1;
        valuedoffix(icount)   = ipresc(inodefix,3);
        fixeddoftable(icount) = dofX;
        icount = icount+1;
        valuedoffix(icount)   = ipresc(inodefix,4);
        fixeddoftable(icount) = dofY;
    elseif  ipresc(inodefix,2)==1
        ifdoffix(dofY)=1;
        icount = icount+1;
        valuedoffix(icount)   = ipresc(inodefix,4);
        fixeddoftable(icount) = dofY;
    elseif  ipresc(inodefix,2)==10
        ifdoffix(dofX)=1;
        icount = icount+1;
        valuedoffix(icount)   = ipresc(inodefix,3);
        fixeddoftable(icount) = dofX;
    elseif  ipresc(inodefix,2)==0
    else
        error('Wrong displacement prescription code in data file')
    end
end
%...create table of free dofs by subtracting the set of fixed dofs
%   from the set of all dofs
ngdof=npoin*ndofn;alldoftable=[1:ngdof]';
freedoftable = setxor(alldoftable,fixeddoftable);
%
% Material properties
%
matprop.young = fscanf(fid, '\nYOUNG_MODULUS = %f', 1);
matprop.yield = fscanf(fid, '\nYIELD_STRESS = %f', 1);
%
% Load vector (point loads only)
%
npload = fscanf(fid,'\nPOINT_LOADS = %d',1);
pload  = fscanf(fid, '\n%d %f %f', [1+ndofn, npload]);
pload  = pload';
%...add point loads to global load vector
F=zeros(ngdof,1);
loadednodes=pload(:,1);
loadeddofs=nodofs(loadednodes,:);
F(loadeddofs) = pload(:,2:3);
%
% Reads deformation amplification factor (for plotting only)
amplfact = fscanf(fid,'\nPLOTTING_AMPLIFICATION_FACTOR = %d',1);
%
% Reads upper and lower bounds of variable coordinates to be optimised
%
nnodevar = fscanf(fid, '\nNODES_WITH_VARIABLE_COORDINATES = %d', 1);
ivar   = fscanf(fid, '\n%d %d %f %f %f %f', [2+2*ndofn, nnodevar]);
ivar   = ivar';varnodes=ivar(:,1);
%...create tables of variable coordinates and corresponding prescribed
%   upper and lower bounds
ifcoordvar = zeros(npoin*ndofn,1); icount = 0;
upperbound=[];lowerbound=[];dofcoordvar=[];
for inodevar = 1:nnodevar
    ipoin=ivar(inodevar,1);
    dofX=nodofs(ipoin,1);dofY=nodofs(ipoin,2);
    if  ivar(inodevar,2)==11
        % both x- and y-coordinates are variable
        ifcoordvar(dofX)=1;
        ifcoordvar(dofY)=1; 
        icount = icount+1;
        lowerbound(icount) = ivar(inodevar,3);
        upperbound(icount) = ivar(inodevar,5);
        dofcoordvar(icount) = dofX;
        icount = icount+1;
        lowerbound(icount) = ivar(inodevar,4);
        upperbound(icount) = ivar(inodevar,6);
        dofcoordvar(icount) = dofY;
    elseif  ivar(inodevar,2)==1
        % only y-coordinate is variable
        ifcoordvar(dofY)=1;
        icount = icount+1;
        lowerbound(icount) = ivar(inodevar,4);
        upperbound(icount) = ivar(inodevar,6);
        dofcoordvar(icount) = dofY;
    elseif  ivar(inodevar,2)==10
        % only x-coordinate is variable
        ifcoordvar(dofX)=1;
        icount = icount+1;
        lowerbound(icount) = ivar(inodevar,3);
        upperbound(icount) = ivar(inodevar,5);
        dofcoordvar(icount) = dofX;
    elseif  ivar(inodevar,2)==0
        disp('WARNING: Node listed with no variable coordinates for optimisation process')
    else
        error('Wrong variable coordinate prescription code in data file')
    end
end
%************************************************************************
%
%                           IMPORTANT
%                 (DEFINIFION OF DESIGN VARIABLES)
%
% set of dofs associated with variable coordinates
dofcoordfix=setxor(alldoftable,dofcoordvar);
if isempty(dofcoordvar)
    disp('No variables in optimisation problem - all nodes have fixed coordinates')
    error('No variables in optimisation problem - all nodes have fixed coordinates')
end
%
% arrange coordinates following dof ordering (in one-dimensional array, as
% in global displacement vector)
coorddof=zeros(ngdof,1);
for ipoin=1:npoin
    dofx=ipoin*2-1;dofy=ipoin*2;
    coorddof(dofx)=coord(ipoin,1);coorddof(dofy)=coord(ipoin,2);
end
% split coordinates array into variable and fixed coordinates
coorddofvar=coorddof(dofcoordvar);coorddoffix=coorddof(dofcoordfix);
%************************************************************************
%
% Store fixed data in structure
fixeddata.amplfact=amplfact;
fixeddata.coorddoffix=coorddoffix;
fixeddata.csarea=csarea;
fixeddata.sndmoa=sndmoa;
fixeddata.dofcoordfix=dofcoordfix;
fixeddata.dofcoordvar=dofcoordvar;
fixeddata.eldofs=eldofs;
fixeddata.F=F;
fixeddata.fixeddoftable=fixeddoftable;
fixeddata.freedoftable=freedoftable;
fixeddata.lnods=lnods;
fixeddata.lowerbound=lowerbound;
fixeddata.matprop=matprop;
fixeddata.ndofn=ndofn;
fixeddata.nelem=nelem;
fixeddata.ngdof=ngdof;
fixeddata.npoin=npoin;
fixeddata.upperbound=upperbound;
fixeddata.valuedoffix=valuedoffix;
%
% Close file(s)
status = fclose(fid);
%
end
%%%%%%%%%%%%%%%%%%%%%%

The input text file is

TITLE = buckling_check_1

ELEMENTS = 9

1  1 2  1.53e-4  0.68e-8
2  2 3  1.53e-4  0.68e-8
3  1 3  1.53e-4  0.68e-8
4  1 4  1.53e-4  0.68e-8
5  3 4  1.53e-4  0.68e-8
6  3 6  1.53e-4  0.68e-8
7  3 5  1.53e-4  0.68e-8
8  4 5  1.53e-4  0.68e-8
9  6 5  1.53e-4  0.68e-8

NODE_COORDINATES = 6
1   0.0  0.0
2   0.0  4.0
3   5.0  4.0
4   5.0  0.0
5   10.0 0.0
6   10.0 4.0

NODES_WITH_PRESCRIBED_DISPLACEMENTS = 2
1  11 0.000 0.000
5  11 0.000 0.000


YOUNG_MODULUS =210000.0

YIELD STRESS =250.0

NODES_WITH_POINT_LOAD = 3
2  0 -100
4  0 -50
6  0 -100


PLOTTING_AMPLIFICATION_FACTOR =10

NODES_WITH_VARIABLE_COORDINATES = 4
2  01 0.1 0.1 1.0 1.5
3  01 0.1 0.1 1.0 1.5
4  01 0.1 0.1 1.0 1.5
6  01 0.1 0.1 1.0 1.5 

Answer 1

[Ameer Hamza]

It turns out that the error is caused by wrong field names in the function truss2D_readdata. Some field names in the text file are a bit different as compared to the function. Change the line

matprop.yield = fscanf(fid, '\nYIELD_STRESS = %f', 1);

to

matprop.yield = fscanf(fid, '\nYIELD STRESS = %f', 1);

and change the line

npload = fscanf(fid,'\nPOINT_LOADS = %d',1);

to

npload = fscanf(fid,'\nNODES_WITH_POINT_LOAD = %d',1);

[Rita Akonobi]

Thanks a lot. There was a change.

I didn't write the code. I'm trying to improve it for my work as my coding is really poor. I have spent days on this.

I feel like crying

Thanks a lot.

[Ameer Hamza]

Glad to be of help. I would also take this opportunity to point to this resource on debugging the MATLAB program: https://www.mathworks.com/help/matlab/matlab_prog/debugging-process-and-features.html. The error message indicates the line at which the error occurred. Just add a breakpoint at that line and see what might be causing the issue. Most of the time, the problem is caused by a trivial mistake.

[Rita Akonobi]

Thanks a lot. Saved the link