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How to round a value to the nearest value in an array?

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Alexandre Nevsky
Alexandre Nevsky on 10 Nov 2020
Answered: Bjorn Gustavsson on 10 Nov 2020
I have a large matrix of orientation values from an image and want to round them to the nearest value from an array.
What I have right now is a very long and overly complicated if/else statement that looks like this:
array = [0, 45, 90, 135];
if ((value(x, y) >= 0 && value(x, y) < 22.5) || (value(x, y) >= 157.5 && value(x, y) < 202.5) || (value(x, y) >= 337.5) && (value(x, y) <= 360))
value(x, y) = array(1);
elseif ((value(x, y) >= 22.5) && (value(x, y) < 67.5) || (value(x, y) >= 202.5) && (value(x, y) < 247.5))
value(x, y) = array(2);
...
end
What I would like is something that resembles more the following, or any MATLAB type shortcut:
array = [0, 45, 90, 135];
value(x, y) = roundToNearest(value(x, y), array);

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Answers (2)

Ameer Hamza
Ameer Hamza on 10 Nov 2020
You can use interp1() with 'nearest'
array = [0, 45, 90, 135];
value; % matrix
value_rounded = interp1(array, array, value, 'nearest', 'extrap')

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Bjorn Gustavsson
Bjorn Gustavsson on 10 Nov 2020
At the file exchange I quickly found a couple of contributions that allows rounding to some desired precision. For this case could you use something like:
y_rounded = 45*round(y_values/45);
HTH

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