Contiguous Number Checking and Verification

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RDG
RDG 2013-7-4
Suppose, I have a variable, a.
a={ 18 5 1 3
14 2 1 2
4 2 5 9
2 1 5 7
1 5 6 7
3 3 6 1
3 7 6 5
16 6 6 3
5 3 6 6};
Based on column 3 value, I would like to check whether the values in COLUMN 4 are contiguous or not. The eg below is elaborated to clarify my goal.
Column 3 contains unique values of 1,5 and 6:
18 5 1 3
14 2 1 2
- The values in column 4 are contiguous
4 2 5 9
2 1 5 7
- The values in column 4 are NOT contiguous. (Missing '8' in Col 4)
1 5 6 7
3 3 6 1
3 7 6 5
16 6 6 3
5 3 6 6
- The values in column 4 are NOT contiguous. (Missing '2','4' in Col 4)
Result: [0 1 2]
How can I perform this complex computation? Ideally, the results should be stored using just 1 variable (if possible). My code at the moment is way too complicated and not efficient. Any help would be greatly appreciated.
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dpb
dpb 2013-7-9
OK, you gave an example of what is/isn't contiguous; that helps.
But, you still haven't shown what is the specific output -- is it just a logical in which case the answer would be [1 0 0]'? Or something else?
Have to have a precise working definition to implement a solution. The general idea outlined previously works; accumarray() likely is your friend here.
RDG
RDG 2013-7-10
It isn't a logical. If you notice, it's 0,1 and 2. 0 because there's no missing value (contiguous), 1 because it's missing the value 8, and 2 because it is missing the value 2 and 4.

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dpb
dpb 2013-7-10
编辑：dpb 2013-7-10
OK, just change the function slightly...
MATL
>> [~,~,c] = unique(a(:,3));
>> nmiss=accumarray(c,a(:,4),[],@(x) length([min(x):max(x)])-length(x))
nmiss =
0
1
2
>>
And, to anticipate the next wishes/needs (*) ...
MATL
>> [u,~,c] = unique(a(:,3));
>> groups = accumarray(c,a(:,4), [length(u) 1], @(x) {x})
groups =
[2x1 double]
[2x1 double]
[5x1 double]
>> groups{:}
ans =
3
2
ans =
9
7
ans =
7
1
5
3
6
>> missing = accumarray(c,a(:,4), [length(u) 1], ...
@(x) {setdiff(min(x):max(x), x)})
missing =
[1x0 double]
[ 8]
[1x2 double]
>> missing{:}
ans =
Empty matrix: 1-by-0
ans =
8
ans =
2 4
>>
(*) And credit to Kelly Kearney at cs-sm who showed the "trick" to getting the SZ argument correct for the cell array addressing for the last two. Thanks, Kelly!!! :)

更多回答（1 个）

dpb
dpb 2013-7-9
Given the input a, the first case of returning a logical array of groups that are/aren't contiguous...
MATL
>> [u,~,c] = unique(a(:,3));
>> lcontig=accumarray(c,a(:,4),[],@(x) all(abs(diff(x))==1))
lcontig =
1
0
0
>>
Again, need more definition to know what you're actually after but should give you some ideas...

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