I built a cell array that contains non-string elements, say, vectors containing numbers.
How can I search if a vector exits in this cell array? Since the elements are not strings, I cannot use ismember() function.
Concretely, if I had a cell array like
a = {[1 2], [2 3], [3 4], [4 5]}
how can I find out if [2 3] is in this cell array?
I think this should work:
find(ismember(cell2mat(a'),[2 3],'rows'));
or if you don't need the location:
any(ismember(cell2mat(a'),[2 3],'rows'));
Good luck =)
You can try this :
ismember(num2str([2 3]), cellfun(#num2str, a, 'UniformOutput', false))
Related
how can I get a matrix out of cell array?
here is my cell array:
d{1} = [[1 1]; [2 2]; [3 3]]
d{2} = [[1 2]; [2 3]]
I want to get the first matrix out of d{1} which should give me [1 1] but I tried this:
d{1}(1) and It only gives me the first element in the cell. How can I get it to return these cells as a matrix?
As you want to access both columns of the first row. So, simply do this: d{1}(1,:)
Think I have an array like
A = { 1,2,3,4,5,6}
I need to get the position of 4 in this array.
I tried,
p = find(A==4)
Please help.
If you really need a cell array (for example because the cells can contain vectors of different sizes):
A = {1, [1 2 3], 4, [1 2], [3 4]}; %// example cell array
sought = [1 2]; %// sought contents
index = find(cellfun(#(x) isequal(x, sought), A));
you created a cell-array instead of a normal vector.
Try:
A = [1,2,3,4,5,6]
find(A==4)
Cell arrays are great to store variables with different types.You could, for example, create a cell array that contains strings as well as digits.
If you have only digits in your array you should defintely use normal arrays.
These are defined by [ ] instead of { }
As you have defined a cell array you need to convert it to a numeric array for find to work, fortunately this is simple to achieve with a couple of well placed brackets.
A = { 1,2,4,3,5,6};
find([A{:}]==4)
ans =
3
So A{:} writes out the numeric values from your array and the [] contains the output for find to work.
p.s. I re-arranged the numbers in A to show that it was working as '4' is now in position 3 to provide a better test.
I have a 3000x1 cell array of vectors of different lengths and am looking for a way to search them all for a number and return the cell indices for the first and last occurrence of that number.
So my data looks like this:
[1]
[1 2]
[1 2]
[3]
[6 7 8 9]
etc
And I want to my results to look like this when I search for the number 1:
ans = 1 3
All the indices (e.g. [1 2 3] for 1) would also work, though the above would be better. So far I'm unable to solve either problem.
I've tried
cellfun(#(x) x==1, positions, 'UniformOutput', 0)
This returns a logical array, effectively putting me back at square 1. I've tried using find(cellfun...) but this gives the error undefined function 'find' for input arguments of type 'cell'. Most of the help I can find is for searching for strings within a cell array. Do I need to convert all my vectors to strings for this to work?
C = {[1]
[1 2]
[1 2]
[3]
[6 7 8 9]}; %// example data
N = 1; %// sought number
ind = cellfun(#(v) any(v==N), C); %// gives 1 for cells which contain N
first = find(ind,1);
last = find(ind,1,'last');
result = [ first last ];
This is probably a super simple question, but here it is:
I have a <1xn> array of structs, and a vector of the indexes of the struct array that I want to remove.
So for example, if I have a removal vector of [2 6], it means I want to get rid of the 2nd and 6th struct in the array (and the array would be 2 elements shorter).
What is the clean, simple, matlab way of doing this?
If the name of your structure is a:
a([2 6])=[]
or more generally:
ind2rm=[2 6];
a(ind2rm)= []
PS: it also works for normal arrays or matrices (e.g. A(:,[2 6])=[])
I think this is what you need:
a = a(setdiff([1:n], [2, 6]))
a is the struct array and [2, 6] are the elements you want to remove.
I would like to sort elements in a comma-separated list. The elements in the list are structs and I would like the list to be sorted according to one of the fields in the struct.
For example, given the following code:
L = {struct('obs', [1 2 3 4], 'n', 4), struct('obs', [6 7 5 3], 'n', 2)};
I would want to have a way to sort L by the field 'n'. Matlab's sort function only works on matrices or arrays and on lists of strings (not even lists of numbers).
Any ideas on how that may be achieved?
Thanks,
Micha
I suggest you do this in three steps: Extract 'n' into an array, sort the array and consequently reorder the elements of the cell array.
%# get the n's
nList = cellfun(#(x)x.n,L);
%# sort the n's and capture the reordering in sortIdx
[sortedN,sortIdx] = sort(nList);
%# use the sortIdx to sort L
sortedL = L(sortIdx)
This is a bit of an aside, but if all of the structures in your cell array L have the same fields (obs and n in this case), then it would make more sense to store L as a 1-by-N structure array instead of a 1-by-N cell array of 1-by-1 structures.
To convert the 1-by-N cell array of structures to a 1-by-N structure array, you can do the following:
L = [L{:}];
Or, you can create the structure array directly using one call to STRUCT instead of creating the cell array of structures as you did in your example:
L = struct('obs',{[1 2 3 4],[6 7 5 3]},'n',{4,2});
Now the solution from Jonas becomes even simpler:
[junk,sortIndex] = sort([L.n]); %# Collect field n into an array and sort it
sortedL = L(sortIndex); %# Apply the sort to L
For what it's worth, here is the solution in Python:
L = [{'n': 4, 'obs': [1, 2, 3, 4]}, {'n': 2, 'obs': [6, 7, 5, 3]}]
L.sort(lambda a,b: a['n'].__cmp__(b['n']))
# L is now sorted as you wanted