I want a column vector that contains only the character A, that is,
A
A
A
A
like this. So i have tried
'A'*ones(4,1)
But in place of A, it takes on value 65. How can i get A ?
You can do it this way:
repmat('A',4,1)
Or use your approach but include char to convert back to string after the multiplication:
char('A'*ones(4,1))
Multiplication of chars with doubles gives doubles; the charis cast to double, using the corresponding ASCII value.
Just cast back to char:
char('A'*ones(4,1))
but probably Luis' answer is faster ;)
Related
I have a problem in general when Matlab is unable to work out how to logically store values of differing uint types. For example:
tempC = {uint8(5) uint16(16)}
For me, it seems logical to be able to convert this into a matrix of type integer using cell2mat(tempC), which returns
>> cell2mat(tempC)
Error using cell2mat (line 45)
All contents of the input cell array must be of the same data type.
Of course, I understand that the truncation behaviour of integers depends on the type (e.g. uint8 forces all numbers greater than 255 to be 255), however, in this case I would say it would be safe enough to output cell2mat(tempC) with uint16 type. Does anyone have any ideas on how this can be achieved in general?
cell2mat will not work if there are cells of differing types. cell2mat merges the cells together into a matrix, but matrix elements in MATLAB must all share the same type. This is fundamental to how MATLAB works with numeric matrices. If you didn't have all of the same type, then you should use cell arrays... which is what they are for.
However, one thing I can suggest is figure out the type of all of the elements in your matrix, then iterate through each cell and cast them all to be the largest precision type. You can then use cell2mat on this intermediate result to complete the conversion. However, what I have written doesn't actually require calling cell2mat in the end. You'll see later.
Something like this:
%// Get all of the possible types in the array
types = unique(cellfun(#class, tempC, 'uni', 0));
%// Figure out the largest type
vals = cellfun(#(x) double(intmax(x)), types);
[~,ind_max] = max(vals);
%// Cast all values to this type
class_max = types{ind_max};
tempC = cellfun(#(x) cast(x, class_max), tempC);
We first determine all of the possible classes that your cell array contains. We then figure out which of the types is the largest of them all. This can be done by using intmax on each of the types. intmax tells you the largest possible integer that is available for that type, so we basically choose the type that generates the largest possible integer. Take note that I had to cast to double as the output of intmax certainly does output the maximum associated for an integer type, but the output is also cast to that type. This is required so that I can combine all of these elements into an array of the same type - double.
Once we get the type producing the maximum possible integer, we then go through the cell array and cast all of the values to this type. Take note that I used cellfun for the final call which outputs a numeric array - no need to use cell2mat here. In the last line of code, I use cast to cast all of the numbers in the cell array to this type, thus achieving "coercion".
Using your example array, this is what I get, as well as what class the final array is in:
>> tempC
tempC =
5 16
>> class(tempC)
ans =
uint16
I'm trying to initialize
labels =['dh';'Dh';'gj';'Gj';'ll';'Ll';'nj';'Nj';'rr';'Rr';'sh';'Sh';'th';'Th';'xh';'Xh';'zh';'Zh';'ç';'Ç';'ë';'Ë'];
But it shows me the error on title.When I try with numbers it's all perfect but not with characters.What could be the problem?
If you wish to eliminate any padding, you can also store it into a cell as follows.
labels = {'dh';'Dh';'gj';'Gj';
'll';'Ll';'nj';'Nj';
'rr';'Rr';'sh';'Sh';
'th';'Th';'xh';'Xh';
'zh';'Zh';'ç';'Ç';
'ë';'Ë'};
Then you can reference the "i"th element using labels{i} instead of labels(i,:) which is simpler. You can further run more string operations using cellfun and not interfere with any existing values that you've stored.
I agree with krisdestruction that using a cell array makes the code accessing the strings simpler and is generally more idiomatic. That is what I would also recommend unless there is a compelling reason to do something else.
For completeness, you could use the char function to add the padding automatically for you if you really want a character array:
>> char('aa','bb','c')
ans =
aa
bb
c
where the last row is 'c '. From the char documentation:
S = char(A1,...,AN) converts the arrays A1,...,AN into a single character array. After conversion to characters, the input arrays become rows in S. Each row is automatically padded with blanks as needed. An empty string becomes a row of blanks.
(Emphasis mine)
From the Mathworks documentation:
Apply the MATLAB concatenation operator, []. Separate each row with a semicolon (;). Each row must contain the same number of characters. For example, combine three strings of equal length:
You can try padding like this to make every row 2 characters:
labels = ['dh';'Dh';'gj';'Gj';
'll';'Ll';'nj';'Nj';
'rr';'Rr';'sh';'Sh';
'th';'Th';'xh';'Xh';
'zh';'Zh';'ç ';'Ç ';
'ë ';'Ë '];
New to Matlab and using the an e-book to learn.
This was the question:
Write a MATLAB program which takes as its input a character string and print out its
penultimate character.
The code I worked out:
A=char('X');
X=input('Please enter a string of characters: ','s');
disp(X(Size-1));
What am I doing wrong?
When I run it, the input part happens and then I get an error, I assume this is due to incorrect index reference?
Thanks
Size is a function, not a variable. Therefore, it would need arguments, like size(X) which would return [1 5] for a 1x5 matrix.
Try X(length(X)-1) or more concisely, X(end-1)
More info:
size(matrix) returns the dimensions of a matrix.
size(matrix, dimension) returns the number of elements in a dimension (row, column, etc) of a matrix.
numel(matrix) returns the number of elements of a matrix. For a 2D matrix, this is #rows * #cols. For any matrix, this is equivalent to prod(size(matrix)).
length(matrix) finds the number of elements along the largest dimension of a matrix. It is equivalent to max(size(matrix))
I want to use xor for my double numbers in matlab,but bitxor is only working for int numbers. Is there a function that could convert double to int in Matlab?
The functions You are looking for might be: int8(number), int16(number), uint32(number) Any of them will convert Double to an Integer, but You must pick the best one for the result You want to achieve. Remember that You cannot cast from Double to Integer without rounding the number.
If I understood You correcly, You could create a function that would simply remove the "comma" from the Double number by multiplying your starting value by 2^n and then casting it to Integer using any of the functions mentioned earlier, performing whatever you want and then returning comma to its original position by dividing the number by 2^n
Multiplying the starting value by 2^n is a hack that will decrease the rounding error.
The perfect value for n would be the number of digits after the comma if this number is relatively small.
Please also specify, why are You trying to do this? This doesn't seem to be the optimal solution.
You can just cast to an integer:
a = 1.003
int8(a)
ans =
1
That gives you an 8 bit signed integer, you can also get other size i.e. int16 or else unsigned i.e. uint8 depending on what you want to do
The data is like this
5.1,3.5,1.4,0.2,Iris-setosa
while I read it using this
data = fscanf(file, '%f,%f,%f,%f,%s');
and it turned out that data is an array of float rather than a combination of float and string. So how do I read this data from txt?
From the Matlab docs for fscanf:
Output Arguments A: An array. If the format includes:
Only numeric specifiers, A is numeric. ... Only character or
string specifiers (%c or %s), A is a character array. ... A
combination of numeric and character specifiers, A is numeric, of
class double. MATLAB converts each character to its numeric
equivalent. This conversion occurs even when the format explicitly
skips all numeric values (for example, a format of '%*d %s').
So your best bet is to read everything in as strings, and then convert the numeric strings to numeric values, using str2num or str2double or similar.
Alternatively, since you know there are 4 floating point values that really store a floating point value, and then the rest store the numeric ASCII values for the string, you can always split up your data and cast the part you know should be a string to char. Something like:
flt = data(1:4);
str = char(data(5:end));