Line of best fit

So I have an assignment where we need to plot data points as a scatterplot and then plot the line of best fit on top of the figure.

I ran into a problem for the last question of the assignment, where we need to do this except with stock closing data that is 252 days long.

    Example:
    A = [10 1;20 1;30 1;40 1;50 1;]
    b = [8;7;4;6;3]
    coeff = A\b
    new = A*coeff

As shown in the example, we are supposed to solve for the coefficients with left division. However, I do not know how to do this without manually typing out the array with a one at the end of each element.

load fordstock
day = linspace(0,252,252);
scatter(day,ford)
axis([0 300 38 50])

one = ones(1,252,1)
XX = [day one;]

Note: This XX array is where I am struggling since it just prints out all of the days first and then all of the ones.

Answer 1

[Star Strider]

Use the ones function:

A = [(10:10:50)' ones(5,1)];
b = [8;7;4;6;3];
coeff = A\b
new = A*coeff

so ‘XX’ should be:

XX = [day(:) ones(252,1)];

You have too many arguments in your ‘one’ vector. (The ‘(:)’ subscript forces a column vector.)