Problem using nlinfit with a multivariable function

I have the following code so far:

clear , clc , clf

% EXPERIMENTAL DATA =======================================================

load('dispvst.mat'); % Reads Data Set 1

X1 = dispvst(:,2); % Time Vector

Y1 = dispvst(:,1); % Displacement Vector

% REGRESSION ==============================================================

beta0 = [1 2];

FIT = nlinfit(X1,Y1,@FUN1,beta0); % Coefficient Fit

% Function ================================================================

function MODELFUN = FUN1(k,c,t)

m = 1; % Mass (kg)

Wn = sqrt(k/m); % Wn

E = c / (2*Wn); % E

Wd = Wn * sqrt(1-E^2); % Wd

A = sqrt((Wn*E*X1(1)) / Wd + X(1)^2); % A

Phi = atan(Wd/(E*Wn)); % Phi

MODELFUN = A*exp(-E*Wn*t)*sin(Wd*t+Phi); % Model Function

end

% END =====================================================================

MatLab gives me the following error code:

%===========================================================================

Error using nlinfit (line 213)

Error evaluating model function 'FUN1'.

Error in HW2P3 (line 16)

FIT = nlinfit(X1,Y1,@FUN1,beta0); % Coefficient Fit

Caused by:

Error using /

Matrix dimensions must agree.

=================================================================================

I can't figure out the correct syntax to use in order to use the function in the nlinfit function

[Patel Mounika]

Can you please share dispvst.mat file.