error in Modal Analysis code from MATLAB

Hi everyone,

I found this MATLAB code in their directory to help me get the frequencies and modes of a MDOF structure. I've inputted all my values into the function but it gives me an error for NM and get an error that says local function must be different than script name. Has anyone used this script before and I'm not sure what I'm doing wrong. Below is the code I'm using:

%% Newmark Function; NM

clear all

clc

load('SineSweep.mat')

g=386.4;

M=[4.3 0 0;0 4.3 0; 0 0 4.3];

K=[4494.6375 -2247.32 0;-2247.32 4494.6375 -2247.32; 0 -2247.32 2247.32];

F=g*M;

ft=AccTopFSW*g;

zet=0;

[phi,omega2]=eig(K,M);

function [disp,EF]=NM(n,nom,dt,F,ft,M,K,zet,omega2,phi)

%% By Newmark Linear Method

Mn=phi'*M*phi;

Kn=phi'*K*phi;

Ln=zeros(nom);

for i=1:nom

Ln(i,i)=(phi(:,i))'*F/Mn(i,i); % Load Contribution Facor

end

u=zeros(length(ft),nom);

v=zeros(length(ft),nom);

ac=zeros(length(ft),nom);

ft(end+1)=0;

for j=1:nom % equation of motion(Newmark linear method)

m=Mn(j,j);

k=Kn(j,j);

c=2*m*(omega2(j,j))^.5*zet/100;

K=k+3*c/dt+6*m/(dt)^2;

a=6*m/dt+3*c;

b=3*m+dt*c/2;

for i=1:length(u)-1

u(1,j)=0; %initial conditions

v(1,j)=0;

ac(1,j)=0;

df=Ln(j,j)*Mn(j,j)*(ft(i+1)-ft(i))+a*v(i,j)+b*ac(i,j); % delta Force

du=df/K;

dv=3*du/dt-3*v(i,j)-dt*ac(i,j)/2;

dac=6*(du-dt*v(i,j))/(dt)^2-3*ac(i,j);

u(i+1,j)=u(i,j)+du;

v(i+1,j)=v(i,j)+dv;

ac(i+1,j)=ac(i,j)+dac;

end

end

ft(end)=[];

%% Combine Modes Then Develop Story Responses

disp=zeros(size(u,1),n); % Story displacement

acc=zeros(size(ac,1),n); % story acceleration

EF=zeros(size(u,1),n); % Story force

for st=1:n % st is story

for j=1:nom % j is mode

disp2=zeros(size(u,1),n);

accel=zeros(size(ac,1),n);

EF1=zeros(size(u,1),n);

disp2(:,st)=phi(st,j)*u(:,j); % Chopra, pp 438; Disp=phi*U

accel(:,st)=phi(st,j)*ac(:,j);

EF1(:,st)=omega2(j,j)*M(st,st)*phi(st,j)*u(:,j); % Chopra, pp 438

disp=disp2+disp; % Displacement of Stories

acc=accel+acc; % Acceleration of Stories

EF=EF1+EF; % Seismic Force of Stories

end

end

end

I'm loading a Sinesweep acceleration data and I;ve inputted most of the values. n=3, nom=3, dt=0.002.

Please and Thank you.

Answer 1

[Manoj Mirge]

In MATLAB scripts the names of local functions and name of script in which local functions are defined must be different. If you have script named “main.mlx” then you cannot define local function named “main” in that script.

It seems like you have script named “NM” and you have defined local function named “NM” in that script and that is causing the error.

You can either change the function name or script name depending upon the use case.

You can read more about local function in below attached link:

https://www.mathworks.com/help/matlab/matlab_prog/local-functions.html