Error using plot; invalid first data argument

%this is my code. it is returning the titular error and I cannot figure out why

data=load('riverspeed.html')

x=data(1,:)
y=data(2,:)
color=input('select color')

symbol=menu('Select symbol','point','circle')
switch symbol
    case 1
        plot(x,y,color,'.')
    case 2
        plot(x,y,color, 'o')
end

%'riverspeed.html' is a random two row matrix

Answer 1

[KSSV]

data=load('riverspeed.html')
x=data(1,:) ;
y=data(2,:) ;
color=input('select color:')
symbol=menu('Select symbol:','point','circle')
switch symbol
    case 1
        plot(x,y,strcat(color,'.'))
    case 2
        plot(x,y,strcat(color,'o'))
end

[Alex Hosmer]

that worked perfectly thank you

Answer 2

[Jan]

Then please explain the type and contents of this first argument.

data = load('riverspeed.html');
x = data(1,:);
class(x)
size(x)
x

What do you get? I guess load('*.html') does not do, what you expect, because load is not designed for HTML files.