I would like to concatenate strings. I tried using strcat:
x = 5;
m = strcat('is', num2str(x))
but this function removes trailing white-space characters from each string. Is there another MATLAB function to perform string concatenation which maintains trailing white-space?
You can use horzcat instead of strcat:
>> strcat('one ','two')
ans =
onetwo
>> horzcat('one ','two')
ans =
one two
Alternatively, if you're going to be substituting numbers into strings, it might be better to use sprintf:
>> x = 5;
>> sprintf('is %d',x)
ans =
is 5
How about
strcat({' is '},{num2str(5)})
that gives
' is 5'
Have a look at the final example on the strcat documentation: try using horizontal array concatination instead of strcat:
m = ['is ', num2str(x)]
Also, have a look at sprintf for more information on string formatting (leading/trailing spaces etc.).
How about using strjoin ?
x = 5;
m ={'is', num2str(x)};
strjoin(m, ' ')
What spaces does this not take into account ? Only the spaces you haven't mentioned ! Did you mean:
m = strcat( ' is ',num2str(x) )
perhaps ?
Matlab isn't going to guess (a) that you want spaces or (b) where to put the spaces it guesses you want.
Related
Input
str = 'test1,test2,test3,'
Ouput
str = 'test1,test2,test3'
Requirement to strip the last occurence of ','
Just use rstrip().
result = your_string.rstrip(',')
str = 'test1,test2,test3,'
str[:-1] # 'test1,test2,test3'
The question is very old but tries to give the better answer
str = 'test1,test2,test3,'
It will check the last character, if the last character is a comma it will remove otherwise will return the original string.
result = str[:-1] if str[-1]==',' else str
Though it is little bit over work for something like that. I think this statement will help you.
str = 'test1,test2,test3,'
result = ','.join([s for s in str.split(',') if s]) # 'test1,test2,test3'
If you have to remove the last comma (also as the last character?) you can do this via the function removesuffix()
Here is an example:
>>>'hello,'.removesuffix(',')
'hello'
Actually we have to consider the worst case also.
The worst case is,
str= 'test1,test2,test3, ,,,, '
for above code, please use following code,
result = ','.join([s.strip() for s in str.split(',') if s.strip()!=''])
It will work/remove the prefix 'comma' also. For example,
str= ' , ,test1,test2,test3, ,,,, '
So say I have a string with some underscores like hi_there.
Is there a way to auto-convert that string into "hi there"?
(the original string, by the way, is a variable name that I'm converting into a plot title).
Surprising that no-one has yet mentioned strrep:
>> strrep('string_with_underscores', '_', ' ')
ans =
string with underscores
which should be the official way to do a simple string replacements. For such a simple case, regexprep is overkill: yes, they are Swiss-knifes that can do everything possible, but they come with a long manual. String indexing shown by AndreasH only works for replacing single characters, it cannot do this:
>> s = 'string*-*with*-*funny*-*separators';
>> strrep(s, '*-*', ' ')
ans =
string with funny separators
>> s(s=='*-*') = ' '
Error using ==
Matrix dimensions must agree.
As a bonus, it also works for cell-arrays with strings:
>> strrep({'This_is_a','cell_array_with','strings_with','underscores'},'_',' ')
ans =
'This is a' 'cell array with' 'strings with' 'underscores'
Try this Matlab code for a string variable 's'
s(s=='_') = ' ';
If you ever have to do anything more complicated, say doing a replacement of multiple variable length strings,
s(s == '_') = ' ' will be a huge pain. If your replacement needs ever get more complicated consider using regexprep:
>> regexprep({'hi_there', 'hey_there'}, '_', ' ')
ans =
'hi there' 'hey there'
That being said, in your case #AndreasH.'s solution is the most appropriate and regexprep is overkill.
A more interesting question is why you are passing variables around as strings?
regexprep() may be what you're looking for and is a handy function in general.
regexprep('hi_there','_',' ')
Will take the first argument string, and replace instances of the second argument with the third. In this case it replaces all underscores with a space.
In Matlab strings are vectors, so performing simple string manipulations can be achieved using standard operators e.g. replacing _ with whitespace.
text = 'variable_name';
text(text=='_') = ' '; //replace all occurrences of underscore with whitespace
=> text = variable name
I know this was already answered, however, in my case I was looking for a way to correct plot titles so that I could include a filename (which could have underscores). So, I wanted to print them with the underscores NOT displaying with as subscripts. So, using this great info above, and rather than a space, I escaped the subscript in the substitution.
For example:
% Have the user select a file:
[infile inpath]=uigetfile('*.txt','Get some text file');
figure
% this is a problem for filenames with underscores
title(infile)
% this correctly displays filenames with underscores
title(strrep(infile,'_','\_'))
I'm reading fixed-width (9 characters) data from a text file using textscan. Textscan fails at a certain line containing the string:
' 9574865.0E+10 '
I would like to read two numbers from this:
957486 5.0E+10
The problem can be replicated like this:
dat = textscan(' 9574865.0E+10 ','%9f %9f','Delimiter','','CollectOutput',true,'ReturnOnError',false);
The following error is returned:
Error using textscan
Mismatch between file and format string.
Trouble reading floating point number from file (row 1u, field 2u) ==> E+10
Surprisingly, if we add a minus, we don't get an error, but a wrong result:
dat = textscan(' -9574865.0E+10 ','%9f %9f','Delimiter','','CollectOutput',true,'ReturnOnError',false);
Now dat{1} is:
-9574865 0
Obviously, I need both cases to work. My current workaround is to add commas between the fields and use commas as a delimiter in textscan, but that's slow and not a nice solution. Is there any way I can read this string correctly using textscan or another built-in (for performance reasons) MATLAB function?
I suspect textscan first trims leading white space, and then parses the format string. I think this, because if you change yuor format string from
'%9f%9f'
to
'%6f%9f'
your one-liner suddenly works. Also, if you try
'%9s%9s'
you'll see that the first string has its leading whitespace removed (and therefore has 3 characters "too many"), but for some reason, the last string keeps its trailing whitespace.
Obviously, this means you'd have to know exactly how many digits there are in both numbers. I'm guessing this is not desirable.
A workaround could be something like the following:
% Split string on the "dot"
dat = textscan(<your data>,'%9s%9s',...
'Delimiter' , '.',...
'CollectOutput' , true,...
'ReturnOnError' , false);
% Correct the strings; move the last digit of the first string to the
% front of the second string, and put the dot back
dat = cellfun(#(x,y) str2double({y(1:end-1), [y(end) '.' x]}), dat{1}(:,2), dat{1}(:,1), 'UniformOutput', false);
% Cast to regular array
dat = cat(1, dat{:})
I had a similar problem and solved it by calling textscan twice, which proved to be way faster than cellfun or str2double and will work with any input that can be interpreted by Matlab's '%f'
In your case I would first call textscan with only string arguments and Whitespace = '' to correctly define the width of the fields.
data = ' 9574865.0E+10 ';
tmp = textscan(data, '%9s %9s', 'Whitespace', '');
Now you need to interweave and append a delimiter that won't interfere with your data, for example ;
tmp = [char(join([tmp{:}],';',2)) ';'];
And now you can apply the right format to your data by calling textscan again with a delimiter like:
result = textscan(tmp, '%f %f', 'Delimiter', ';', 'CollectOutput', true);
format shortE
result{:}
ans =
9.5749e+05 5.0000e+10
Comparing the speed of this approach with str2double:
n = 50000;
data = repmat(' 9574865.0E+10 ', n, 1);
% Approach 1 with str2double
tic
tmp = textscan(data', '%9s %9s', 'Whitespace', '');
result1 = str2double([tmp{:}]);
toc
Elapsed time is 2.435376 seconds.
% Approach 2 with double textscan
tic
tmp = textscan(data', '%9s %9s', 'Whitespace', '');
tmp = [char(join([tmp{:}],';',2)) char(59)*ones(n,1)]; % char(59) is just ';'
result2 = cell2mat(textscan(tmp', '%f %f', 'Delimiter', ';', 'CollectOutput', true));
toc
Elapsed time is 0.098833 seconds.
I have a problem in Octave
I want to find all different(!) pairs of two letters in a text(with no spaces, only letters)
For example:
my text = "abcdabcd"
i want find array(or vector?) that looks like: ab bc cd da
How do i do this in the easies way possible?
Thanks for your help
You can use the unique() function to do this. The only trick is in creating the list of two characters which can be done by using two lines, shifted by one character.
str = "abcdabcd";
str(2,:) = shift (str, -1);
str(:,end) = []; # remove last column
unique (str', "rows")
I'm trying to write a simple function that takes two inputs, x and y, and passes these to three other simple functions that add, multiply, and divide them. The main function should then display the results as a string containing x, y, and the totals.
I think there's something I'm not understanding about output arguments. Anyway, here's my (pitiful) code:
function a=addxy(x,y)
a=x+y;
function b=mxy(x,y)
b=x*y;
function c=dxy(x,y)
c=x/y;
The main function is:
function [d e f]=answer(x,y)
d=addxy(x,y);
e=mxy(x,y);
f=dxy(x,y);
z=[d e f]
How do I get the values for x, y, d, e, and f into a string? I tried different matrices and stuff like:
['the sum of' x 'and' y 'is' d]
but none of the variables are showing up.
Two additional issues:
Why is the function returning "ans 3" even though I didn't ask for the length of z?
If anyone could recommend a good book for beginners to MATLAB scripting I'd really appreciate it.
Here's how you convert numbers to strings, and join strings to other things (it's weird):
>> ['the number is ' num2str(15) '.']
ans =
the number is 15.
You can use fprintf/sprintf with familiar C syntax. Maybe something like:
fprintf('x = %d, y = %d \n x+y=%d \n x*y=%d \n x/y=%f\n', x,y,d,e,f)
reading your comment, this is how you use your functions from the main program:
x = 2;
y = 2;
[d e f] = answer(x,y);
fprintf('%d + %d = %d\n', x,y,d)
fprintf('%d * %d = %d\n', x,y,e)
fprintf('%d / %d = %f\n', x,y,f)
Also for the answer() function, you can assign the output values to a vector instead of three distinct variables:
function result=answer(x,y)
result(1)=addxy(x,y);
result(2)=mxy(x,y);
result(3)=dxy(x,y);
and call it simply as:
out = answer(x,y);
As Peter and Amro illustrate, you have to convert numeric values to formatted strings first in order to display them or concatenate them with other character strings. You can do this using the functions FPRINTF, SPRINTF, NUM2STR, and INT2STR.
With respect to getting ans = 3 as an output, it is probably because you are not assigning the output from answer to a variable. If you want to get all of the output values, you will have to call answer in the following way:
[out1,out2,out3] = answer(1,2);
This will place the value d in out1, the value e in out2, and the value f in out3. When you do the following:
answer(1,2)
MATLAB will automatically assign the first output d (which has the value 3 in this case) to the default workspace variable ans.
With respect to suggesting a good resource for learning MATLAB, you shouldn't underestimate the value of the MATLAB documentation. I've learned most of what I know on my own using it. You can access it online, or within your copy of MATLAB using the functions DOC, HELP, or HELPWIN.
I just realized why I was having so much trouble - in MATLAB you can't store strings of different lengths as an array using square brackets. Using square brackets concatenates strings of varying lengths into a single character array.
>> a=['matlab','is','fun']
a =
matlabisfun
>> size(a)
ans =
1 11
In a character array, each character in a string counts as one element, which explains why the size of a is 1X11.
To store strings of varying lengths as elements of an array, you need to use curly braces to save as a cell array. In cell arrays, each string is treated as a separate element, regardless of length.
>> a={'matlab','is','fun'}
a =
'matlab' 'is' 'fun'
>> size(a)
ans =
1 3
I was looking for something along what you wanted, but wanted to put it back into a variable.
So this is what I did
variable = ['hello this is x' x ', this is now y' y ', finally this is d:' d]
basically
variable = [str1 str2 str3 str4 str5 str6]