what is the 'ro' in plot() mean?

I saw this:

plot(x,y,'ro')

I checked the doc but didn't find it. What does 'ro' mean? Thanks.

[Stephen23]

This is the LineSpec: the help explains what it is, and gives all options:

http://www.mathworks.com/help/matlab/ref/linespec.html

http://www.mathworks.com/help/matlab/ref/plot.html#inputarg_LineSpec

Answer 1

[John D'Errico]

READ THE HELP! The important part is here:

Various line types, plot symbols and colors may be obtained with
    plot(X,Y,S) where S is a character string made from one element
    from any or all the following 3 columns:

             b     blue          .     point              -     solid
             g     green         o     circle             :     dotted
             r     red           x     x-mark             -.    dashdot 
             c     cyan          +     plus               --    dashed   
             m     magenta       *     star             (none)  no line
             y     yellow        s     square
             k     black         d     diamond
             w     white         v     triangle (down)
                                 ^     triangle (up)
                                 <     triangle (left)
                                 >     triangle (right)
                                 p     pentagram
                                 h     hexagram

r and o are both listed as doing something independent of each other.

[Binzi Shu]

So I can combine them, like "go", "b." etc?

[Image Analyst]

Yes, you can string together one from each column in a single quoted string. You can leave one or two out if you want, so you can have up to three (or 4) characters in the string, like 'ro-', 'ro', 'b--', 'mx-.', etc.