How do you use values from an array as serial numbers to extract values from a different array?

If I am using an array to record values such as [0:10:100], then how can I create a column vector containing values extracted from a table(with two columns, one of which is the independent variable and the other is the dependent variable) with the intervals 0, 10, 20,...,100?

Answer 1

[Star Strider]

It is not possible to reference ‘row 0’ since MATLAB subscripts begin at 1.

I am not certain what you want, so see if this short example works for you:

T1 = array2table(randi(100, 35, 2));                    % Create Random Table
T2ext = T1([1 10:10:30],:);                             % Extract Rows

.

[Vedeesh Bali]

I'll be more specific. I have a table of values corresponding from 15 to 120 (like 15 is 9.3, 16 is 9.7,..., 150 is 677.2) and an array called vfit = [15:5:150], and I have to extract a column vector containing estimated values of the array vfit.

[Star Strider]

I am still not exactly certain what result you want.

Try this:

M = [15:150; rand(size(15:150))].'                      % Create Matrix
vfit = 15:5:150;                                        % Create 1vfit’

Lv = ismember(M(:,1), vfit);                            % Logical Vector
Out = [vfit(:) M(Lv, 2)]                                % Result

Note that this assumes that the array (here ‘M’) is a (136x2) matrix.

[Vedeesh Bali]

I think I can explain now.

If one of the values 'x' present in vfit also exists in my imported table, I want to extract the 'y=f(x)' values corresponding to the table.

Eg: if I have this table

x1 y1

x2 y2

. .

. .

. .

xn yn

And x2 and xn belong to vfit, how can I create an array containing y2 and yn?

[Star Strider]

My final suggestion is to use interp1:

yi = interp1(x, y, vfit)
Out = [vfit, yi]

That will likely produce the result you want, even though I still have no idea what that is. Note that for this to work, both ‘x’ and ‘vfit’ must be monmotonically either increasing or decreasing, and both must go in the same direction.