Graphing multiple unique points in a line

Hi!

I'm writing a code in a for loop that is meant to find the value of "m" for various differnt values of theta. For each range of theta, the equation for m and the variables needed to find m may change. The problem I am having is that I can only get my code to graph points and not a line. Each point is a differnt color so it seems like my code is treating them as unique values. How do I get them to graph into a line? Heres the code a snippet of code:

for theta = 0 : pi/24 : pi
    if (0 <= theta) && (theta < pi/4)
        p = 5;
        h = .09 * sin(theta);
        x = .09 * cos(theta);
        b = asin(h / .2);
        x1 = .2 * cos(b);
        f = (p / cos(b));
        cy = f * sin(b);
        m = cy * (x + x1);
    elseif (pi/4 <= theta) && (theta <= pi/2)
        p = (28/pi)*(theta-(pi/4))+5;
        h = .09 * sin(theta);
        x = .09 * cos(theta);
        b = asin(h / .2);
        x1 = .2 * cos(b);
        f = (p / cos(b));
        cy = f * sin(b);
        m = cy * (x + x1);
    elseif (pi/2 < theta) && (theta <= pi)
        p = (6/pi)*(theta-pi/2)+12;
        h = .09 * sin(theta);
        x = .09 * cos(theta);
        b = asin(h / .2);
        x1 = .2 * cos(b);
        f = (p / cos(b));
        cy = f * sin(b);
        m = cy * (x + x1);
    end
    hold on;
    plot(theta, m, 'o')
    hold off;
end

If you plot this it just does dots, since I have 'o', but if I change it to '-k' the graph goes blank. Please help!

Thanks in advance

[Rena Berman]

(Answers Dev) Restored edit

Answer 1

[Walter Roberson]

thetavals = 0 : pi/24 : pi;
for thetaidx = 1 : length(thetavals)
    theta = thetavals(thetaidx);
    if (0 <= theta) && (theta < pi/4)
        p = 5;
        h = .09 * sin(theta);
        x = .09 * cos(theta);
        b = asin(h / .2);
        x1 = .2 * cos(b);
        f = (p / cos(b));
        cy = f * sin(b);
        m(thetaidx) = cy * (x + x1);
    elseif (pi/4 <= theta) && (theta <= pi/2)
        p = (28/pi)*(theta-(pi/4))+5;
        h = .09 * sin(theta);
        x = .09 * cos(theta);
        b = asin(h / .2);
        x1 = .2 * cos(b);
        f = (p / cos(b));
        cy = f * sin(b);
        m(thetaidx) = cy * (x + x1);
    elseif (pi/2 < theta) && (theta <= pi)
        p = (6/pi)*(theta-pi/2)+12;
        h = .09 * sin(theta);
        x = .09 * cos(theta);
        b = asin(h / .2);
        x1 = .2 * cos(b);
        f = (p / cos(b));
        cy = f * sin(b);
        m(thetaidx) = cy * (x + x1);
    else
        error('theta invalid')
    end
    hold on;
    plot(thetavals, m, 'o')
    hold off;
end

I recommend that you learn how to use logical indexing.

[Sean McLafferty]

Thanks Walter! This helped a lot. To be honest I dont even know what logical indexing is, so I will definetly look into it. Have a good weekend