Fill in the callback function so that it gets the value of the slider, prints that value in the text box, and uses it to set the LineWidth of the plot (so, e.g., if the slider value is its maximum, the line width of the plot would be 5)

sliderlinewidth.m

function sliderlinewidth

f = figure('Visible', 'off','Position',[20,20,500,400]); 

slhan = uicontrol('Style','slider','Units','Normalized',...

 'Position',[.3 .3 .4 .1], ...

 'Min', 1, 'Max', 5,'Value',3,'Callback', @callbackfn); 

slval = uicontrol('Style','text',...

 'Units','Normalized','Position', [.4 .1 .2 .1]); 

axhan = axes('Units', 'Normalized','Position', [.3 .5 .4 .3]);

x = -2*pi:0.1:2*pi;

y = cos(x);

phan = plot(x,y)

set(f,'Visible','on');

 function callbackfn(source,eventdata)

 num=get(slhan, 'Value');

 set(slval, 'String',num2str(num))

 set(phan,'LineWidth',num)

 end

end