I am receiving an "Illegal use of the reserved keyword 'if'" in my code. It is working fine on all the previous 'if(isempty...)' and then outputing the error on the last statement. Does anyone have any advice?

echo off
%See notes of pg389/656 of Vibration Simulation Textbook

clf;
clear all;

inp=input('Input "1" to enter beam dimensions, "Enter" to use default...');

if (isempty(inp))
  inp=0;
else
end

if inp==0

wbeam=2
tbeam=0.2
lbeam=20
E=190*10^6
density=7.83*10^-6

else

%input size of beam and material

wbeam=input('Input width of beam, default 2mm,...');

if (isempty(wbeam))
  wbeam=2;
else
end

tbeam=input('Input thickness of beam, default 0.2mm,...');

if (isempty(tbeam))
  tbeam=0.2;
else
end

lbeam=input('Input thickness of beam, default 20mm,...');

if (isempty(lbeam))
  lbeam=20;
else
end

E=input('Input modulus of material, mN/mm^2, default stainless steel 190e6...');

if (isempty(E))
  E=190*10^6
else
end

density=input('Input density of material, kg/mm^3, default stainless steel 7.83e-6...');

if (isempty(density))
  density=7.83*10^-6;
else
end

end

%input number of elements

num_elements=input('Input number of elements for beam, minimum 2, default 10...');

if (isempty(num_elements))
  num_elements=10;
else
end

%define whether or not to do Guyan Reduction

guyan=input('enter "1" to do Guyan elimination of rotations,..., "enter" to not do Guyan...')

if (isempty(guyan))
  guyan=0;
else
end

if guyan==0

  num_plot_max=2*num_elements;
  num_plot_default=num_elements;
  
else

  num_plot_max=num_elements;
  num_plot_default=num_elements;
end

num_plot=input(['enter the number of modes to plot,max',...num2str(num_plot_max,',default',num2str(num_plot_default),'...']);

if (isempty(num_plot))
    num_plot=9;
else
end

Answer 1

[Walter Roberson]

Your "..." in your num_plot is the continuation operator, everything after it is a comment.

num_plot=input(['enter the number of modes to plot,max',...
  num2str(num_plot_max),',default',num2str(num_plot_default),'...']);

[Shawn Saunders]

Thanks