why do I get this "Matrix dimensions must agree" error ?

Hi there

every time I ran this code and chose another item of listbox rather than the first item, I see this :

Matrix dimensions must agree.

Error in testp>ButtonPushed (line 17)

if a=='Bisection'

please help !

my code :

function v
fig = uifigure;
tg = uitabgroup(fig,'Position',[190 150 200 200]);
t = uitab(tg,'Title','input information');
bb = uieditfield(t,'text','Position',[11 145 150 22],'Value','input function like: x.^2');
dd = uidropdown(t,'Position',[11 90 150 22],'Items',{'Bisection','false position','Newton & Rophson'...
    'Secant'});
t.Scrollable = 'on';
btn = uibutton(fig,'push',...
               'Position',[11 40 140 22],'Text','start',...
               'ButtonPushedFcn', @(btn,event) ButtonPushed(btn,dd));
           
end
function ButtonPushed(btn,dd)
       
        a=dd.Value;
        if a=='Bisection'
            xl=input('xl ra vared konid = ');
            xu=input('xu ra vared konid = ');
            Bisection(xl,xu)
        elseif a=='false position'
            xl=input('xl ra vared konid = ');
            xu=input('xu ra vared konid = ');
            Nabejaee(xln,xu)
            elseif a=='Newton & Rophson'
            xi=input('xi ra vared konid = ');
            L=input('karan paeen tabe jahat rasm ra vared konid = ');
            U=input('karan balaye tabe jahat rasm ra vared konid = ');
            Newton_Rophson(xi,L,U)
                elseif a=='Secant'
            xi_old=input('xi-1 ra vared konid = ');
            xi=input('xi ra vared konid = ');
            L=input('karan paeen tabe jahat rasm ra vared konid = ');
            U=input('karan balaye tabe jahat rasm ra vared konid = ');
            Secant_m(xi_old,xi,L,U)
            
        end
end

Answer 1

[Walter Roberson]

Use strcmp() to compare character vectors.