MATLAB won't plot my graph

So I'm trying to get the following code to plot on a graph:

for x = -3.0:0.1:3.0
    for y = -3.0:0.1:3.0
        for z = power((sin(x.*y)),2)
            figure
            if (z < 0.1)
            plot(x,y, 's', 'b')
            hold
            elseif (z >= 0.1 && z < 0.5)
            plot(x,y, 's', 'c')
            hold
            elseif (z >= 0.5 && z < 0.75)
            plot(x,y, 's', 'g')
            hold
            elseif (z >= 0.75 && z < 0.95)
            plot(x,y, 's', 'r')
            hold
            else
            plot(x,y, 's', 'k')
            hold
            end
        end
    end
end

And it keeps throwing "Error using plot Invalid first data argument" at me I'm not quite sure why, considering in the first iteration of the loop, x and y are only defined as one number, not a vector.

Any help would be appreciated.

Answer 1

[Walter Roberson]

When you use two quoted strings like that, plot (at least in R2014a) tries to interpret the 's' as being the name of a property. If you are trying to use 's' as the marker shape and then a separate color, then you need to either combine the two into a single linespec like 'sb' or else you need to switch over to using a name/value pair like 's', 'color', 'b' or the fuller 'marker', 's', 'color', 'b'

Answer 2

[Jason Allnutt]

Also, you're "figure" command and the individual "hold" commands gave me trouble when I tested your code. In the sample I have provided I removed the "figure" call and moved a single "hold on" command to the beginning of the script.

Not sure if the outcome is what you expected but please run it and let me know.

hold on
for x = -3.0:0.1:3.0
    for y = -3.0:0.1:3.0
        for z = power((sin(x.*y)),2)
            if (z < 0.1)
                plot(x,y, 'sb')
            elseif (z >= 0.1 && z < 0.5)
                plot(x,y, 'sc')
            elseif (z >= 0.5 && z < 0.75)
                plot(x,y, 'sg')
            elseif (z >= 0.75 && z < 0.95)
                plot(x,y, 'sr')
            else
                plot(x,y, 'sk')
            end
        end
    end
end