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how can i remove an array from an array?

How can I remove duplicates in an array but keep the same order?

  • I have this cell array in MATLAB: y = { 'd' 'f' 'a' 'g' 'g' 'a' 'w' 'h'} I use unique(y) to get rid of the duplicates but it rearranges the strings in alphabetical order: >> unique(y) ans = 'a' 'd' 'f' 'g' 'h' 'w' I want to remove the duplicates but keep the same order. I know I could write a function do do this but was wondering if there was a simpler way using unique to remove duplicates while keeping the same order just with the duplicates removed. I want it to return this: >> unique(y) ans = 'd' 'f' 'a' 'g' 'w' 'h'

  • Answer:

    Here's one solution that uses some additional input and output arguments that http://www.mathworks.com/access/helpdesk/help/techdoc/ref/unique.html has: >> y = { 'd' 'f' 'a' 'g' 'g' 'a' 'w' 'h'}; %# Sample data >> [junk,index] = unique(y,'first'); %# Capture the index, ignore junk >> y(sort(index)) %# Index y with the sorted index ans = 'd' 'f' 'a' 'g' 'w' 'h'

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If you look at the documentation for http://www.mathworks.com/access/helpdesk/help/techdoc/ref/unique.html, there's the option to return an index along with the sorted array. You can specify whether you want the first or last occurrence of a number to be returned to the index as well. For example: a=[5, 3, 4, 2, 1, 5, 4]; [b,order]=unique(a,'first') returns b=[1, 2, 3, 4, 5] and m=[5, 4, 2, 3, 1] You can sort your order array and store the index next [~,index]=sort(order) %# use a throw-away variable instead of ~ for older versions and finally re-index b b=b(index)

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