I have some which converts a cell array of strings into a cell array of characters.
Note. For a number of reasons, both the input (C) and the output (C_itemised) must be cell arrays.
The cell array of strings (C) is as follows:
>> C(1:10)
ans =
't1416933446'
''
't1416933446'
''
't1416933446'
''
't1416933446'
''
't1416933446'
''
I have only shown a portion of the array here. In reality it is ~28,000 rows in length.
I have some code which does this, although it is very inefficient. The cellstr function takes up 72% of the code's time, as it is currently called thousands of times. The code is as follows:
C_itemised=cell(length(C),500);
for i=3:length(C)
temp=char(C{i});
for j=1:length(temp)
C(i-2,j)=cellstr(temp(j));
end
end
I have a feeling that some minor modifications could take out the inner loop, thus cutting down the overall running time substantially. I have tried a number of ways to do this, but I think I keep getting confused about whether to use {} or (), and haven't been able to find anything online that can help me. Can anyone see a way to make the code more efficient?
Please also note that this function is used in conjunction with other functions, and does work, although it is running slower than would be ideal. Therefore, I do not wish to change the format of C_itemised.
EDIT:
(A sample of) the output of my current function is:
C_itemised(1,1:12)
ans =
Columns 1 through 12
't' '1' '4' '1' '6' '9' '3' '3' '4' '4' '6' []
One thing I can suggest is to use the undocumented function sprintfc. This function is hidden from normal use in MATLAB, but it is used internally with a variety of other functions. Mainly, if you tried doing help sprintfc, it'll say that there's no function found! It's cool to sniff around the source sometimes!
How sprintfc works is that you provide it a formatting string, much like printf, and the data you want printed. It will take each individual element in the data and place them into individual cell arrays. As an example, supposing I had a string D = 'abcdefg';, if we did:
out = sprintfc('%c', D);
We get:
>> celldisp(out)
out{1} =
a
out{2} =
b
out{3} =
c
out{4} =
d
out{5} =
e
out{6} =
f
out{7} =
g
As such, it takes each element in your string and places them as individual characters serving as individual elements in a new cell array. The %c formatting string means that we want to print a single character per element. Check out the link to Undocumented MATLAB that I posted above if you want to learn more!
Therefore, try simplifying your loop to this:
C_itemised=cell(length(C));
for i=1:length(C)
C_itemised{i} = sprintfc('%c', C{i});
end
C_itemised will be a cell array, where each element C_itemised{i} is another cell array, with each element in this cell array being a single character that is composed of the string C{i}.
Minor Note
You said you were confused about {} and () in MATLAB for cells. {} is used to access individual elements inside the cell. So doing C{1} for example will grab whatever is stored in the first element of the cell array. () is used to slice and index into the cells. For example, if you wanted to make another cell array that is a subset of the current one, you would do something like C(1:3). This will create a three element cell array which is composed of the first three cells in C.
Related
I have data stored in text files.The data is in 'cell array of string' after read it using textscan and contains various of colour name. Below is the content of my data:
name of colour
'lavender'
'lavenderblush'
'lemonchiffon'
'lightblue'
'lightcoral'
'lightcyan'
I want to create new array to group all color characters into the main color only (red, blue, orange, brown,etc).
I am really struggling to solve this problem. Thank you in advance for any help.
load_data = fopen('result.txt', 'r');
C = textscan(load_data, ' %s ');
fclose(load_data);
name = C{1,1};
group = char(name)
if group{:,1} == lavender
fprintf('purple');
else
fprintf('nothing');
end
This is my code but if I run this, always get error
Cell contents reference from a non-cell array object.
From your comment above, I assume you're having trouble with your code, not actually with the sorting of colors, or how to categorize them.
group is not a Cell array, it's a Char array. So in order to access its values you should use group(:,1) instead of group{:,1}
Remember that the number of columns in group is the number of characters in that line, normalized to the number of characters of the largest string in that set. So 2 issues here:
You can't use group(:,1), as it will get the first character of all the strings in that array. You should get the entire line for that string group(1,:). NB: I say string for simplicity, it's actually a char array.
'lavender' has only 10 characters, but it will have 15, as per the largest string. So the string comparison doesn't quite work, unless you add the extra blank spaces to compensate
You can try out the code below:
load_data = fopen('result.txt', 'r');
C = textscan(load_data, ' %s ');
fclose(load_data);
name = C{1,1};
if name{1,:} == '''lavender'''
fprintf('purple');
else
fprintf('nothing');
end
I assume that your TXT file actually has the string 'lavender', in this case I used character escape '''lavender'''.
The error you are getting is fairly clear. Once you have called char(name), you are working with a regular character array (i.e. a string) and no longer a cell array. Braces (i.e. {}) are used to index cell arrays so you should instead be using parentheses (i.e. ()). Note this actually happens as soon as you index using {} so C{1,1} would actually return a string already and the char line is thus redundant:
if group(:,1) == lavender
I suspect you actually want something more like
name = C{1};
group = char(name) %this line is redundant because C{1} already extracts a string
if strcmp(group,lavender)
fprintf('purple');
else
fprintf('nothing');
end
but it's impossible to say since you did not define the variable lavender.
I would also question what data structure you intend to use. I'm going to assume you actually have some way of categorizing the colours? I'm going to assume this is manual in which case I would suggest converting your txt file to a csv file and putting your manual colour categories as a second column but I'll leave the implementation details to you.
Lets say you have 3 colour categories for now, 'purple', 'blue', and 'orange', my suggestion is to use a logical matrix that has 3 columns (1 per colour category) and n rows where n is the number of rows in your text file (i.e. the number of colours you need to categorize).
Now I'm going to assume you have some sort of mapping function that can categorize your colours so map('lavender') returns 'purple' and map('lightcyan') returns 'blue'
First we should make a cell array of categories that we can use to map the category string to its column number:
categories = {'purple'
'blue'
'orange'}
and the result will go in the logical matrix categorized
load_data = fopen('result.txt', 'r');
C = textscan(load_data, ' %s ');
fclose(load_data);
n = numel(C);
categories = {'purple'
'blue'
'orange'};
categorized = false(n, numel(categories)); %preallocation
for row = 1:n
colour = C{row};
category = map(colour); %you need to implement this map function yourself.
categorized(row, strcmp(category, categories)) = true;
end
I have a cell array. Some of the elements in this cell array contains zeros as the first character and the whole element is only numbers (double) as well. When exporting these to Excel (which I prefer), the zeros are deleted and converting it to a number.
Let's take an example to illustrate my problem. I have a cell array with 10 elements:
NodeID = {'0000006';
'0000011';
'000011R';
'000016R';
'000021R';
'B276_2';
'EB 7.55';
'EB2521';
'EllebaekOPlB1';
'EllebaekOplB10'};
The first two elements contains zeros until the number 6 and 11, respectively. Unlike the third element and so forth, where letters are involved. So when exporting NodeID to Excel, it returns this in a column (I use writetable command by the way):
6
11
000011R
000016R
000021R
B276_2
EB 7.55'
EB2521
EllebaekOPlB1
EllebaekOplB10
Notice the removal of zeros for the first two elements. Now I know that in Excel, it will keep all the content with the addition of a quote symbol ' in front of the cell, eg. '0000006 for the first element.
I have searched in many places to find a solution to this. But is there a good way to avoid this from happening? Either by somehow adding an extra ยด or some other magical trick which I have not seen?
Thank you in advance!
One alternative (if your values are in a cell, as you say they are):
filename = 'NodeID.xlsx';
NodeID2 = cellfun(#(C) ['''',C], NodeID,'UniformOutput', false)
xlswrite(filename, NodeID2)
This gives you:
NodeID2 =
''0000006'
''0000011'
''000011R'
''000016R'
''000021R'
''B276_2'
''EB 7.55'
''EB2521'
''EllebaekOPlB1'
''EllebaekOplB10'
And an Excel file looking like this:
The cellfun line is equivalent to:
for ii = 1:numel(NodeID)
NodeID2{ii,1} = ['''', NodeID{ii}];
end
The part ['''', NodeID{ii}] inserts a single quotation mark in front for the string. Relevant answer.
I am trying to create a string array which will be fed with string values read from a text file this way:
labels = textread(file_name, '%s');
Basically, for each string in each line of the text file file_name I want to put this string in 10 positions of a final string array, which will be later saved in another text file.
What I do in my code is, for each string in file_name I put this string in 10 positions of a temporary cell array and then concatenate this array with a final array this way:
final_vector='';
for i=1:size(labels)
temp_vector=cell(1,10);
temp_vector{1:10}=labels{i};
final_vector=horzcat(final_vector,temp_vector);
end
But when I run the code the following error appears:
The right hand side of this assignment has too few values to satisfy the left hand side.
Error in my_example_code (line 16)
temp_vector{1:10}=labels{i};
I am too rookie in cell strings in matlab and I don't really know what is happening. Do you know what is happening or even have a better solution to my problem?
Use deal and put the left hand side in square brackets:
labels{1} = 'Hello World!'
temp_vector = cell(10,1)
[temp_vector{1:10}] = deal(labels{1});
This works because deal can distribute one value to multiple outputs [a,b,c,...]. temp_vector{1:10} alone creates a comma-separated list and putting them into [] creates the output array [temp_vector{1}, temp_vector{2}, ...] which can then be populated by deal.
It is happening because you want to distribute one value to 10 cells - but Matlab is expecting that you like to assign 10 values to 10 cells. So an alternative approach, maybe more logic, but slower, would be:
n = 10;
temp_vector(1:n) = repmat(labels(1),n,1);
I also found another solution
final_vector='';
for i=1:size(labels)
temp_vector=cell(1,10);
temp_vector(:,1:10)=cellstr(labels{i});
final_vector=horzcat(final_vector,temp_vector);
end
I have two cell arrays, the sizes are 1x20033 and 1x19. Let's call these two cell arrays as A and B. I want to compare each cell of A with each cell of B to see if there is any common element.
Finally, I need to build a binary matrix and put one when there is a match.
I tried this:
BinaryMatrix=zeros(20033,19);
for i=1:1:20033
for j=1:1:19
match=find(ismember(A{i},B{j}));
if match==1
BinaryMatrix(i,j)= 1;
end
end
end
but I faced this error: "Input A of class double and input B of class cell must be
cell arrays of strings, unless one is a string."
Please tell me What should I do to solve it?
The code that you have almost works. What I would recommend you do is split up the strings found in A and B by spaces. As such, A and B would then be cell arrays of elements where each element in A or B is a single word. The spaces will serve as delimiters for separating out the words.
Once you do this, use intersect to see if there are any common words between the words in A and the words in B. intersect works by considering two arrays (these can be numeric arrays, cell arrays, etc.) C and D as sets, and it returns the set intersection between these two arrays.
In our case, C and D would be a cell array of words separated by spaces from A and B. intersect(C,D) will return a cell array of strings where each element in the output is a string found in both C and D. As such, should this cell array be non-empty, we have found at least one common word between C and D. If this is the case, then set your binary flag at the location of your matrix to 1. In other words:
BinaryMatrix = false(20033,19);
for i=1:1:20033
for j=1:1:19
Asplit = strsplit(A{i});
Bsplit = strsplit(B{j});
if (~isempty(intersect(Asplit, Bsplit)))
BinaryMatrix(i,j)= true;
end
end
end
You'll notice that I have changed your matrix from zeros(20033,19), to false(20033,19). The reason why is because by doing zeros, you are allocating 8 bytes per number in your matrix as this will create your matrix in double precision. By doing false, this will be a logical matrix instead, and you are allocating 1 byte per number. Seeing as how you want BinaryMatrix to be either true or false, don't use double - use logical. I don't know how large both cell arrays are, and so doing this will cut down your memory consumption by 8.
Minor Note
strsplit is only available from R2013a and onwards. If you have a version of MATLAB that is R2012b and lower, replace strsplit with regexp. As such, you would replace the two lines in the for loop with:
Asplit = regexp(A{i}, ' ', 'split');
Bsplit = regexp(B{j}, ' ', 'split');
This is my first time posting so i hope you can help me. I am trying to write a function in matlab.
I have laded data from a file into a cell array. First column contains statements and the second contains T for true og F for false. I now want to split this array into a cell array with the statements and a logical vector with 1 for True and -1 for false.
I use the fgetl within a loop to read all the lines into the cellarray
Try to write it a bit more neatly next time, and consider including a small example.
Here is what you seem to be looking for:
Suppose you have a matrix M and want to split that into M_true and M_false
M = {1,'T';
22,'F';
333,'T'}
idx_T=strcmp(M(:,2),'T')
M_true = M(idx_T,1)
M_false = M(~idx_T,1)