I have a numeric array sized 1000x1 which have values 0 and 1, called conditionArray.
I have a cell array called netNames with the same size (1000x1) and its cells contain string values (which are name of some circuit nets).
I want to extract net names which from netNames which their pairwise condition bit is 1 in conditionArray.
E.g. if conditionArray(100) is equal to extract its net name from netNames{100}.
Output of this process can be stored in an string array or cell array.
Are there any ways to do this operation with pairwise operations or I should use a for statement for this?
You shall check out cellfun in Matlab anytime you want to manipulate each element inside a cellarray without using a for loop.
As I understand, you have:
N = 1000;
% an array with 0s and 1s (this generates random 0s and 1s):
conditionArray = randi([0,1],N);
% a cell array with strings (this generates random 5-character strings):
netNames = cell(N);
netNames = cellfun(#(c)char(randi([double('a'),double('z')],1,5)), netNames, 'UniformOutput',false);
To extract the elements from netNames where conditionArray is 1, you can do:
netNames(conditionArray==1)
This uses logical indexing into the cell array.
Related
I have a column matrix and a cell array which has two columns.The first column has 1x2 doubles and the second column has 1x1 doubles.
For example
columnMatrix = [1;5];
cellArray = {[1,8],[10];[8,1],[20];[4,6],[80];[3,5],[40];[14,16],[85];[5,10],[36]};
I would like to search each element of columnMatrix in cellArray(:,1) and then return its corresponding value in cellArray(:,2)
For example the output has to be like this
newCell = {[1],[10,20];[5],[40,36]};
I tried using the ismember function in this way
[~,idx] = ismember(cell2mat(cellArray(:,1)),columnMatrix (: , 1));
This returns all the indices which have the searched element but they are in two seperate columns and I can not perform any other logical operation to get the corresponding second column entry.
Is there some way this operation can be achieved? Could some one please help?
Thanks
First of all, convert first column of cellArray to a matrix so it would be easier to search values in. Then iterate over columnMatrix values (e.g. using arrayfun, but you could also use for loop), find rows that match (any across columns) and select corresponding values from the second column of cellArray, converting to numeric array ([cellArray{...,2}]). Finally, append the columnMatrix as the first column of the resulting cell array:
columnMatrix = [1;5]; cellArray = {[1,8],[10];[8,1],[20];[4,6],[80];[3,5],[40];[14,16],[85];[5,10],[36]};
mat = cell2mat(cellArray(:,1));
values = arrayfun(#(x) [cellArray{any(mat==x,2),2}], columnMatrix, 'uni', false);
result = [num2cell(columnMatrix), values];
I have a query which I am trying to solve
I know that one can use strcmp(s1,s2) to compare two different strings to see whether they are the same. It gives 1 if that is the case.
However, how would one tackle this problem if you have a variable length array full of strings and you want to the whether all strings in the array are the same.
For example: ['NACA64A010' 'NACA64A010' 'NACA64A010' 'NACA64A010'] we can see that all the strings are the same in this array. However, how would one go about with using strcmp(s1,s2).
Thanks guys!
If you want all pairwise comparisons between strings: call ndgrid to generate indices of all combinations, and then index into your cell array of strings and call strcmp:
x = {'NACA64A010' 'NACA64A010' 'NACA64A010' 'NACA64A010'};
[ii, jj] = ndgrid(1:numel(x));
result = strcmp(x(ii), x(jj));
In this case
result =
1 1 1 1
1 1 1 1
1 1 1 1
1 1 1 1
because all strings are the same.
You probably had a pairwise comparison using strcmp in mind, but you can use it directly on cell arrays:
x={'NACA64A010' 'NACA64A010' 'NACA64A010' 'NACA64A010'}
result=all(strcmpi(x{1},x(2:end)))
Compare the first element to the remaining elements. It returns true only if all elements are equal. For a pairwise comparison you could us:
[~,~,c]=unique(x);
result=bsxfun(#eq,c,c.')
If you're solving the problem with a matrix (i.e. every row is a string) there are no particularly nice solutions in my opinion, but if your strings are contained into a cell array, things are getting easier and nicer.
So we start by creating such cell array:
myStrings={'NACA64A010' 'NACA64A010' 'NACA64A010' 'NACA64A010'};
where each cell contains a string. This will make your code more robust as well since every string can have a different length (this is not true if you concatenate all your strings in a matrix).
Then you specify which string you want to find inside such cell array:
stringThatMustBeTested='NACA64A010';
Now you can use cellfun(), which is a function that applies another function to every cell of a given cell array as follows:
results=cellfun(#(x) strcmp(x,stringThatMustBeTested),myStrings);
Such line simply means "apply strcmp() to every generic cell x inside myStrings and compare the cell with stringThatMustBeTested".
Variable results will be a logical output in which element j will be true if the j-th cell in your cell array is equal to the string you want to test. If results is entirely composed by 1s (which you can check as if sum(results)==length(results)), then all the strings are the same in myStrings (given that stringThatMustBeTested is the unique string in your cell array but anyways, this solution can be extended to a broader string search inside a cell).
In MATLAB, have an N-dimensional cell C, where N is an integer only determined at runtime. How do I access a specific element of C with a vector variable id? For example, with N=3 and id=[1,5,2], how to programmatically get the content of c{1,5,2}? I cannot hard-code it as c{id(1),id(2),id(3)} since N is only fixed at runtime.
If id is a cell array, then you can use sub2ind for this by taking advantage of the comma separated list syntax ,i.e. {:}, to send a variable number of inputs to sub2ind
id = {1,5,2};
ind = sub2ind(size(C), id{:})
c{ind}
if id isn't a cell array (and for some reason can't be created as one), then use num2cell to convert it.
I have a two arrays within a <1x2 cell>. I want to permute those arrays. Of course, I could use a loop to permute each one, but is there any way to do that task at once, without using loops?
Example:
>> whos('M')
Name Size Bytes Class Attributes
M 1x2 9624 cell
>> permute(M,p_matrix)
This does not permute the contents of the two arrays within M.
I could use something like:
>> for k=1:size(M,2), M{k} = permute(M{k},p_matrix); end
but I'd prefer not to use loops.
Thanks.
This seems to work -
num_cells = numel(M) %// Number of cells in input cell array
size_cell = size(M{1}) %// Get sizes
%// Get size of the numeric array that will hold all of the data from the
%// input cell array with the second dimension representing the index of
%// each cell from the input cell array
size_num_arr = [size_cell(1) num_cells size_cell(2:end)]
%// Dimensions array for permuting with the numeric array holding all data
perm_dim = [1 3:numel(size_cell)+1 2]
%// Store data from input M into a vertically concatenated numeric array
num_array = vertcat(M{:})
%// Reshape and permute the numeric array such that the index to be used
%// for indexing data from different cells ends up as the final dimension
num_array = permute(reshape(num_array,size_num_arr),perm_dim)
num_array = permute(num_array,[p_matrix numel(size_cell)+1])
%// Save the numeric array as a cell array with each block from
%// thus obtained numeric array from its first to the second last dimension
%// forming each cell
size_num_arr2 = size(num_array)
size_num_arr2c = num2cell(size_num_arr2(1:end-1))
M = squeeze(mat2cell(num_array,size_num_arr2c{:},ones(1,num_cells)))
Some quick tests show that mat2cell would prove to be the bottleneck, so if you don't mind indexing into the intermediate numeric array variable num_array and use it's last dimension for an equivalent indexing into M, then this approach could be useful.
Now, another approach if you would like to preserve the cell format would be with arrayfun, assuming each cell of M to be a 4D numeric array -
M = arrayfun(#(x) num_array(:,:,:,:,x),1:N,'Uniform',0)
This seems to perform much better than with mat2cell in terms of performance.
Please note that arrayfun isn't a vectorized solution as most certainly it uses loops behind-the-scenes and seems like mat2cell is using for loops inside its source code, so please do keep all these issues in mind.
I have a cell matrix with 2 rows - sorted cell array of different strings and array of numbers. Also I have an example string. It's guarantied that this string appears in the 1st row in the cell array. I want to get index of example's appearance in cell array of strings.
Is there any function in Matlab, that provides solving with logarithmic complexity (something like binary search)?
If you look at ismember code (type open ismember), you'll see that it basically
Checks if the array is sorted (by calling issorted);
If not, it sorts the array;
Then it applies binary search.
So you can directly use ismember.
Example:
>> strings = {'a', 'aa', 'be', 'day', 'yes'};
>> [tf, loc ] = ismember('day', strings);
>> loc
loc =
4
Or maybe modify ismember (save it with another name) to bypass step 1, since you already know your array is sorted.