How to adjust data

I have some data form the height of a waterrocket. I want to compare them using a graph but not all the data starts at the same height so i want to lower the graph so that x0=0 and y0=0. I believe this should do the trick:

Yaxis = [11:1:20]           % Some data
Yaxis = Yaxis-Yaxis(1,1)    % Subtract the first number form every point on the graph

And when i run this in the Command Window it works but when i implement this in my function it doesnt work, what is wrong?

Answer 1

[Jan]

A bold guess: Maybe because you overwrite Yaxis(1,1) before?

Yaxis(1,1) = Yaxis(1,2);
Yaxis      = Yaxis-Yaxis(1,1);

Simplify your code. E.g.:

i = 2;
Yaxis = data. data(2,9);        %zet een begin waarde voor B en data. data(1,9) kan hier niet gebruikt worden omdat dit een extremen waarde is
while i < Rowcount              %Dit moet nog verbetert worden want nu moet handmatig opzoeken hoe veel metingen de sensor heeft gedaan
    A = data. data(i,9) - data. data(2,9);  %Omdat de sensor niet altijd op nul begint berekent dit stuk eerst het verschil tussen de waarde
    Yaxis = [Yaxis A];              %Maakt een array van het verschil 
    i = i + 1;              %Verhoogt i zodat de while loop continued
end

% Simpler without a loop:
Y     = data.data(:, 9);
Yaxis = [Y(2), Y(2:end) - Y(2)];

[Dirk te Brake]

After i tried to use the code you suggested i cant get my code to run. I keep getting the error:

Undefined function 'Dataselectie' for input arguments of type

'char'.

Maybe you know how to fix this?

Thank you for trying to help.

[Jan]

The file Dataselectie.m must be visible for Matlab: either it must be inside the current folder or inside a folder, which is part of Matlab's path. See:

doc path
doc addpath