I have a struct in MATLAB with the size 46x6, the fields are:
name, folder, date, bytes, isdir, datenum
Now I want all 46 entries of name. However, the MATLAB function getfield(structname, 'name') only returns the first entry.
How can I get all elements of the struct?
Name holds strings
If you want the results as a cell array you can call {structname(:).name}.
To return an array you can call [structname(:).name].
First I had to convert the Struct to a cell, and then access it with round brackets
tmp = struct2cell(mystruct)
tmp(1,:)
for i = 1:numel(structname)
name(i)= structname(i).name;
end
Related
I have a table named cellName of size 10000*1. Each entry is a character string of cell names. Each cell name is of different length.
And I want to coerce it into a vector with 10000 elements. How can i do that in matlab? It should be very easy as that in r but i didn't find such command in matlab.
OR: I used readtable to load the 10000*1 table from csv file at the very beginning. It would be great if I can directly read the 10000*1 entries as a single vector too. This is what i did at first.
cellName = readtable('cell.csv');
cellName=cellName(1:10000,1);
Thank you in advance!
Clear example: A is a table of 5*1.
A= apple
banana
pear
peach
watermelon
And i want to coerce A into a vector of 5 elements: A=[apple,banana,pear,peach,watermelon] instead of a table
If a character cell array is what you want, I may have your answer. I also suggest you to read how to access data in a table.
readtable returns a Matlab table data type when succeeded. The table can be accessed like struct with your column name as the fieldname, or be indexed by {} operator like you would access a cell array.
In your example, assuming A is the return value of readtable and your
A = table({'apple','banana','pear','peach','watermelon'}','variableNames',{'cellName'})
Then you can either call
cellName = A.cellName
or
cellName = A{:,1}
to get your cell array.
I have a dataset that I would like to categorise and store in a structure based on the value in one column of the dataset. For example, the data can be categorised into element 'label_100', 'label_200' or 'label_300' as I attempt below:
%The labels I would like are based on the dataset
example_data = [repmat(100,1,100),repmat(200,1,100),repmat(300,1,100)];
data_names = unique(example_data);
%create a cell array of strings for the structure fieldnames
for i = 1:length(data_names)
cell_data_names{i}=sprintf('label_%d', data_names(i));
end
%create a cell array of data (just 0's for now)
others = num2cell(zeros(size(cell_data_names)));
%try and create the structure
data = struct(cell_data_names{:},others{:})
This fails and I get the following error message:
"Error using struct
Field names must be strings."
(Also, is there a more direct method to achieve what I am trying to do above?)
According to the documentation of struct,
S = struct('field1',VALUES1,'field2',VALUES2,...) creates a
structure array with the specified fields and values.
So you need to have each value right after its field name. The way you are calling struct now is
S = struct('field1','field2',VALUES1,VALUES2,...)
instead of the correct
S = struct('field1',VALUES1,'field2',VALUES2,...).
You can solve that by concatenating cell_data_names and others vertically and then using {:} to produce a comma-separated list. This will give the cells' contents in column-major order, so each field name fill be immediately followed by the corresponding value:
cell_data_names_others = [cell_data_names; others]
data = struct(cell_data_names_others{:})
I have a structure in Matlab, each field contains elements with varying numbers of variables. I would like to remove duplicates of numbers that appear within the same field: I know the unique() function and know how to use it to scan through fields one at a time but not an entire field.
I think I want something like:
structure(1:length(structure)).field=unique(structure(1:length(structure)).field
and get
original
field=[1,2,3] [1,4,5] [2,5,8]
to turn into
field=[1,2,3] [4,5] [8]
Maybe a complicated for loop similar to below (isn't working) which would grab the values from the first element in the field, search through each additional element, and if that value is present set it equal to =[];, and iterate through that way?
for n=1:length(RESULTS)
for m=1:length(RESULTS(n).Volumes)
for l=1:length(RESULTS)
for o=1:length(RESULTS(l).Volumes)
if RESULTS(n).Volumes(m)==RESULTS(l).Volumes(o)
RESULTS(l).Volumes(o)=[];
end
end
end
end
end
Thanks!
This is a quick-and-dirty attempt, but you might be able to improve on it. Assume your struct array and field are sa(:).v. I'm also assuming that the field contains a 1xn array of numbers, as in your example. First, make a "joint" array with the concatenation of all field values and filter the non-unique values:
joint = cell2mat({sa.v});
[uniqJoint,~,backIdx] = unique(joint);
The "uniqJoint" array has also been sorted, but the "backIdx" array contains the indices that, if applied to uniqJoint, will rebuild the original "joint" array. We need to somehow connect those to the original indices (i,j) into the struct array and within the field value sa(i).v(j). To do that, I tried creating an array of the same size as "joint" that contains the indices of the struct that originally had the corresponding element in the "joint" array:
saIdx = cell2mat(arrayfun(#(i) i * ones(1,length(sa(i).v)), ...
1:length(sa), 'UniformOutput', false));
Then you can edit (or, in my case, copy and modify the copy of) the struct array to set the field to the values that have not appeared before. To do that, I keep a logical array to mark the indices of "backIdx" as "already used", in which case I skip those values when rebuilding the fields of each struct:
sb = sa;
used = false(length(backIdx));
for i = 1:length(sa)
origInd = find(saIdx == i); % Which indices into backIdx correspond to this struct?
newInd = []; % Which indices will be used?
for curI = backIdx(origInd)
if ~used(curI)
% Mark as used and add to the "to copy" list
used(curI) = true;
newInd(end+1) = curI;
end
end
% Rewrite the field with only the indices that were not used before
sb(i).v = uniqJoint(newInd);
end
In the end, the data in sb(i).v contains the same numbers as sa(i).v without repeats, and removing those that appeared in any previous elements of the struct.
I have a cell array that is a list of file names. I transposed them because I find that easier to work with. Now I am attempting to go through each line in each cell and remove the lines based on their file extension. Eventually, I want to use this list as file names to import data from. This is how I transpose the list
for i = 1:numel(F);
a = F(1,i);
b{i} = [a{:}'];
end;
The code I am using to try and read the data in each cell keeps giving me the error input must be of type double or string. Any ideas?
for i = 1:numel(b);
for k = 1:numel(b{1,i});
b(cellfun(textscan(b{1,i}(k,1),'%s.lbl',numel(b)),b))=[];
end;
end;
Thanks in advance.
EDIT: This is for MATLAB. Should have been clear on that. Thanks Brian.
EDIT2: whos for F is
Name Size Bytes Class Attributes
b 1x11 13986188 cell
while for a is
Name Size Bytes Class Attributes
a 1x1 118408 cell
From your description I am not certain how your F array looks, but assuming
F = {'file1.ext1', 'file2.ext2', 'file3.ext2', 'file2.ext1'};
you could remove all files ending with .ext2 like this:
F = F(cellfun('isempty', regexpi(F, '\.ext2$')));
regexpi, which operates on each element in the cell array, returns [] for all files not matching the expression. The cellfun call converts the cell array to a logical array with false at positions corresponding to files ending with .ext2and true for all others. The resulting array may be used as a logical index to F that returns the files that should be kept.
You're using cellfun wrong. It's signature is [A1,...,Am] = cellfun(func,C1,...,Cn). It takes a function as first argument, but you're passing it the result of textscan, which is a cell array of the matching strings. The second argument is a cell array as it should be, but it doesn't make sense to call it over and over in a loop. `cellfun´'s job is to write the loop for you when you want to do the same thing to every cell in a cell array.
Instead of parsing the filename yourself with textscan, I suggest you use fileparts
Since you're already looping over the cell array in transpose-step, it might make sense to do the filtering there. It might look something like this:
for i = 1:numel(F);
a = F(1,i);
[~,~,ext] = fileparts(a{:});
if strcmpi(ext, '.lbl')
b{i} = [a{:}'];
end
end;
I have a struct array Imgs and it includes following properties of image files inside each struct.
name
date
byte
isdir
datenum
now I want to create a new string array img_names that includes the only names of the above struct array. I am really a newbie about matlab and I don't get how to do it.
So I want to have a array like in that structure.
img_names[1] = 'file-1.jpg'
img_names[2] = 'file-2.jpg'
img_names[3] = 'file-3.jpg'
...
img_names = arrayfun(#(x) x.name,Imgs,'uni',false)
produces a cell array containing the names. You can then access each name using:
img_names{1}
img_names{2}
% ...
>> img_names=sprintf('%s\n',Imgs.name);