Finding nearest low match in array
44 Ansichten (letzte 30 Tage)
Ältere Kommentare anzeigen
Sac
am 4 Apr. 2016
Kommentiert: Kuifeng
am 4 Apr. 2016
Hello, I’m trying to find the nearest match of a value in an array, with the condition that it never rounds up. To explain what I mean, imagine a vector of
f= [1:0.5:5]
where I want to find the nearest low match of 2.3. To simply find the nearest match, I would use
val = 2.3
tmp = abs(f-val)
[i i] = min(tmp)
nearest = f(idx)
How do I reformulate this so it gives me the index of 2 instead? Any tips?
Note, I want it to handle exact matches and negative values as well.
0 Kommentare
Akzeptierte Antwort
Image Analyst
am 4 Apr. 2016
There may be a more compact way of doing it but I'm doing it in explicit separate steps with a ton of comments so that you can easily understand it:
% Define target value.
targetValue = 2.3
% Define test values. This is just for demo, you'd use your actual values.
testValues = 5 * rand(1, 10)
% Find differences
diffValues = testValues - targetValue
% We only want values less than the target value
% so those diffValues will be negative.
% We want the max of those, so set the others to -inf
diffValues(diffValues > 0) = -inf;
% Now we can find the index of the greatest value that
% is still less than the reference value.
[~, indexOfMax] = max(diffValues)
% Get the value from the testValues array
maxValue = testValues(indexOfMax)
Weitere Antworten (3)
Kuifeng
am 4 Apr. 2016
bigger_value_location = find((f-val)>0);
nearest = f(bigger_value_location(1)-1)
3 Kommentare
Kuifeng
am 4 Apr. 2016
you are welcome. pls accept this answer if it's ok. Note (1) f values need to be sorted from small to big
Guillaume
am 4 Apr. 2016
Bearbeitet: Guillaume
am 4 Apr. 2016
A simple way would be to set any value below 0 in your tmp to Inf, before calling min:
f = [1 1.5 2.5 3 2 4.5 5.5 5]; %shuffled values to show that ordering does not matter
val = 2.3;
tmp = val - f;
tmp(tmp < 0) = Inf;
[~, loc] = min(tmp)
0 Kommentare
Azzi Abdelmalek
am 4 Apr. 2016
f= [1:0.5:5]
val = 2.3
[ii,jj]=sort(f)
ii1=find(ii>val,1)-1
idx=jj(ii1)
0 Kommentare
Siehe auch
Kategorien
Mehr zu Loops and Conditional Statements finden Sie in Help Center und File Exchange
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!