If loop issue help

Hello everyone, Im trying to evaluate "Acceleration_Value" and categoryze them as 1, 2 or 3 to depending on thei're value. Im having the issue that ds_mapping an array, stays completly full of 0, what am i doing wrong?

Acceleration_Value= abs(Acceleration); % Obtaining absolute values for acceleration/deceleration

ds_mapping=zeros(size(Acceleration)); % Creating variable to store evaluated values

i= ds ;

if 0.7 <= i & i>= 2.79 %#ok<AND2>

ds_mapping= 1;

elseif 2.79 < i & i >= 3.63 %#ok<AND2>

ds_mapping= 2;

elseif 3.63 < i & i >= 6.5 %#ok<AND2>

ds_mapping= 3;

end

[Jan]

There are no "if loops" in any programming language I know.

[Ricardo jose]

the "if" condition then. By looking code can you understand what im struggling with?

Answer 1

[Star Strider]

An easier way to code that is to use an anonymous function:

ds_mapping = @(i) ((0.7 <= i) &  (i>= 2.79 )).*1 + ((2.79 < i) &  (i >= 3.63 )).*2 + ((3.63 < i) & (i >= 6.5 )).*3;

ds = linspace(0, 7);

figure
plot(ds, ds_mapping(ds))
grid

See the documentation on Anonymous Functions for details.

Answer 2

[Jan]

The if command is not a loop. It requires a scalar condition. You provide vectors, so Matlab inserts an all() automatically.

The "%#ok<AND2>" seems to show, that you have ignored another hint of the editor already: The case 0.7 <= i & i>= 2.79 canbe simplified to i >= 2.79. The same happens for the other branches. It is a good idea not to disable the warnings, but to fix the reason of the warnings.

Do you mean:

if 0.7 <= i &  i <= 2.79 
    %                ^  not > ?!  Same in the other cases
end

Solution: Either create a loop or use logical indexing. With the data you have posted, both will not run:

ds_mapping=zeros(size(Acceleration));        % Creating variable to store evaluated values
i= ds ;

What is ds ?

[Ricardo jose]

ds is a "diff(time)"

[Jan]

You did not mention a variable called "time" yet...