how to find mode without built-in mode function?

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dana
dana 2013-6-9
评论： the cyclist 2021-1-7
any suggestions how to write a function that finds a vectors mode WITHOUT using the built-in mode function?

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回答（3 个）

the cyclist
the cyclist 2013-6-9
You could use the hist() function, and use the value that has the highest count.
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the cyclist
the cyclist 2021-1-7
I think this is because by default, hist() chooses the bin centers by an algorithm that does not guarantee they are in the original vector. Try this instead:
[counts, centers] = histcounts(YourVector,[unique(YourVector) Inf]);
[~, maxidx] = max(counts);
mode_value = centers(maxidx);
the cyclist
the cyclist 2021-1-7
I realized that that code will not find all the modes, if there are multiple. This code should:
[counts, centers] = histcounts(YourVector,[unique(YourVector) Inf]);
max_value = max(counts);
max_idx = (counts==max_value);
mode_values = centers(max_idx)

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Walter Roberson
Walter Roberson 2013-6-9
unique(), take the third output, put it through accumarray(), find the max()
Roger Stafford
Roger Stafford 2013-6-9
编辑：Roger Stafford 2013-6-9
If you are not allowed to use the 'mode' function, it sounds as though you must use only more primitive functions. Are you allowed to do the following with v as the given column vector?
u = sort(v);
f = find([true;diff(u)~=0;true]);
[~,ix] = max(diff(f));
m = u(f(ix)); % m is most frequent value occurring in v
(Corrected)
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Rik
Rik 2021-1-6
Ran in:
That depends on the dimensions of v. If it is a column vector this runs without error.
v = [9;4;2;4;9;2;4];
u = sort(v);
[true;diff(u)~=0;true]
ans = 8x1 logical array
1 0 1 0 0 1 0 1
v = [9;4;2;4;9;2;4];
v = v.';
u = sort(v);
[true;diff(u)~=0;true]
Error using vertcat
Dimensions of arrays being concatenated are not consistent.
Louise Wade
Louise Wade 2021-1-7
编辑：Louise Wade 2021-1-7
I'll try and transpose my row vector into a column vector and try again. If there are multiple values as the mode, would this cause an issue?
EDIT: It seems to be working for me. Thank you so much for helping. All I needed to do was transpose the array.

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