Unique values in an array, with specific digits

Hi, I have an array of 7 digit numbers. i want to count the number of occurrences of unique values starting with two digits, say, 12*****. How can I do that? What about if I want to calculate the frequency of unique values ending with two specific digits, say, *****12?

To calculate unique occurrences for all values, the following works:

a = unique(input)

output = [a,histc(input(:),a)]

Any suggestions would be appreciated! Thanks!

Sushma

Answer 1

[sushma sharma]

close, but not quite. while it lists the unique combinations of first and last digits, how can i get the frequency of each? e.g. count of numbers that begin with the digits 12 (12*****) and count of numbers ending with the digits 12 (e.g. *****12). any help would be appreciated! thank you!

sushma

[Sean de Wolski]

You have to use all of the outputs from unique

[uv,~,idx] = unique(...)
n = accumarray(idx,1)

uv n

Answer 2

[Sean de Wolski]

Starting in R2016b this is much easier with the string class.

x = [1234; 1256; 1334]
s = string(x)
unique(extractBefore(s,3)) % First two
unique(reverse(extractBefore(reverse(s),3))) % Last two

In older releases:

% First two
unique(cellfun(@(x)x(1:2),cellstr(num2str(x)),'uniformoutput',false))

% Last two
unique(cellfun(@(x)x(end-1:end),cellstr(num2str(x)),'uniformoutput',false))