I have been sent some complete MATLAB script. It appears that author of this code has made a specific instruction using num2str and set_param .
What is the purpose of the following line:
['[' num2str(operating_point) ']']
I am interested specially of an intention of using '[' as syntax.
set_param(system_block_name, operating_point_name,...
['[' num2str(operating_point) ']']
In MATLAB rectangular braces [] create vector/matrix.
By default, horizontal vector of strings concatenated into 1 string:
['str1','str2'] % produces str1str2
So
['[',']'] % will print []
num2str() converts number into string:
a=10;
my_str = ['[',num2str(a),']'] % will assign my_str = '[10]'
set_param() is some function that gets 3 parameters, where 3rd one is your string
Related
How can I iterate over a string in Python (get each character from the string, one at a time, each time through a loop)?
As Johannes pointed out,
for c in "string":
#do something with c
You can iterate pretty much anything in python using the for loop construct,
for example, open("file.txt") returns a file object (and opens the file), iterating over it iterates over lines in that file
with open(filename) as f:
for line in f:
# do something with line
If that seems like magic, well it kinda is, but the idea behind it is really simple.
There's a simple iterator protocol that can be applied to any kind of object to make the for loop work on it.
Simply implement an iterator that defines a next() method, and implement an __iter__ method on a class to make it iterable. (the __iter__ of course, should return an iterator object, that is, an object that defines next())
See official documentation
If you need access to the index as you iterate through the string, use enumerate():
>>> for i, c in enumerate('test'):
... print i, c
...
0 t
1 e
2 s
3 t
Even easier:
for c in "test":
print c
Just to make a more comprehensive answer, the C way of iterating over a string can apply in Python, if you really wanna force a square peg into a round hole.
i = 0
while i < len(str):
print str[i]
i += 1
But then again, why do that when strings are inherently iterable?
for i in str:
print i
Well you can also do something interesting like this and do your job by using for loop
#suppose you have variable name
name = "Mr.Suryaa"
for index in range ( len ( name ) ):
print ( name[index] ) #just like c and c++
Answer is
M r . S u r y a a
However since range() create a list of the values which is sequence thus you can directly use the name
for e in name:
print(e)
This also produces the same result and also looks better and works with any sequence like list, tuple, and dictionary.
We have used tow Built in Functions ( BIFs in Python Community )
1) range() - range() BIF is used to create indexes
Example
for i in range ( 5 ) :
can produce 0 , 1 , 2 , 3 , 4
2) len() - len() BIF is used to find out the length of given string
If you would like to use a more functional approach to iterating over a string (perhaps to transform it somehow), you can split the string into characters, apply a function to each one, then join the resulting list of characters back into a string.
A string is inherently a list of characters, hence 'map' will iterate over the string - as second argument - applying the function - the first argument - to each one.
For example, here I use a simple lambda approach since all I want to do is a trivial modification to the character: here, to increment each character value:
>>> ''.join(map(lambda x: chr(ord(x)+1), "HAL"))
'IBM'
or more generally:
>>> ''.join(map(my_function, my_string))
where my_function takes a char value and returns a char value.
Several answers here use range. xrange is generally better as it returns a generator, rather than a fully-instantiated list. Where memory and or iterables of widely-varying lengths can be an issue, xrange is superior.
You can also do the following:
txt = "Hello World!"
print (*txt, sep='\n')
This does not use loops but internally print statement takes care of it.
* unpacks the string into a list and sends it to the print statement
sep='\n' will ensure that the next char is printed on a new line
The output will be:
H
e
l
l
o
W
o
r
l
d
!
If you do need a loop statement, then as others have mentioned, you can use a for loop like this:
for x in txt: print (x)
If you ever run in a situation where you need to get the next char of the word using __next__(), remember to create a string_iterator and iterate over it and not the original string (it does not have the __next__() method)
In this example, when I find a char = [ I keep looking into the next word while I don't find ], so I need to use __next__
here a for loop over the string wouldn't help
myString = "'string' 4 '['RP0', 'LC0']' '[3, 4]' '[3, '4']'"
processedInput = ""
word_iterator = myString.__iter__()
for idx, char in enumerate(word_iterator):
if char == "'":
continue
processedInput+=char
if char == '[':
next_char=word_iterator.__next__()
while(next_char != "]"):
processedInput+=next_char
next_char=word_iterator.__next__()
else:
processedInput+=next_char
In Excel there is a function called clean(), which removes all nonprintable characters from text. Reference https://support.microsoft.com/en-us/office/clean-function-26f3d7c5-475f-4a9c-90e5-4b8ba987ba41#:~:text=Removes%20all%20nonprintable%20characters%20from,files%20and%20cannot%20be%20printed.
I am wondering if there is any direct function/method in python to achieve the same.
Also, how can I mimic clean() function in python just using Regular expression?
Any pointer will be very helpful
The CLEAN function in Excel removes only "the first 32 nonprinting characters in the 7-bit ASCII code (values 0 through 31)", according to the documentation you link to, so to mimic it, you can filter characters of a given string whose ord values are less than 32:
def clean(s):
return ''.join(c for c in s if ord(c) < 32)
Or you can use a regular expression substitution to remove characters with hex values between \x00 and \x1f:
import re
def clean(s):
return re.sub(r'[\x00-\x1f]+', '', s)
I have a few lines of text like this:
abc
def
ghi
and I want to assign these multiple lines to a Matlab variable for further processing.
I am copying these from very large text file and want to process it in Matlab Instead of saving the text into a file and then reading line by line for processing.
I tried to handle the above text lines as single string but am getting an error whilst trying to assign to a variable:
x = 'abc
def
ghi'
Error:
x = 'abc
|
Error: String is not terminated properly.
Any suggestions which could help me understand and solve the issue will be highly appreciated.
I frequently do this, namely copy text from elsewhere which I want to hard-code into a MATLAB script (in my case it's generally SQL code I want to manipulate and call from MATLAB).
To achieve this I have a helper function in clipboard2cellstr.m defined as follows:
function clipboard2cellstr
str = clipboard('paste');
str = regexprep(str, '''', ''''''); % Double any single quotes
strs = regexp(str, '\s*\r?\n\r?', 'split');
cs = sprintf('{\n''%s''\n}', strjoin(strs, sprintf('''\n''')));
clipboard('copy', cs);
disp(cs)
disp('(Copied to Clipboard)')
end
I then copy the text using Ctrl-c (or however) and run clipboard2cellstr. This changes the contents of the clipboard to something I can paste into the MATLAB editor using Ctrl-v (or however).
For example, copying this line
and this line
and this one, and then running the function generates this:
{
'For example, copying this line'
'and this line'
'and this one, and then running the function generates this:'
}
which is valid MATLAB which can be pasted directly in.
Your error is because you ended the line when MATLAB was expecting a closing quote character. You must use array notation to have multi-line or multi-element arrays.
You can assign like this if you use array notation
x = ['abc'
'def'
'hij']
>> x = 3×3 char array
Note: with this method, your rows must have the same number of characters, as you are really dealing with a character array. You can think of a character array like a numeric matrix, hence why it must be "rectangular".
If you have MATLAB R2016b or newer, you can use the string data type. This uses double quotes "..." rather than single quotes '...', and can be multi-line. You must still use array notation:
x = ["abc"
"def"
"hijk"]
>> x = 3×1 string array
We can have different numbers of characters in each line, as this is simply a 3 element string array, not a character array.
Alternatively, use a cell array of character arrays (or strings)
x = {'abc'
'def'
'hijk'}
>> x = 3×1 cell array
Again, you can have character arrays or strings of different lengths within a cell array.
In all of the above examples, a newline is simply for readability and can be replaced by a semi-colon ; to denote the next line of the array.
The option you choose will depend on what you want to do with the text. If you're reading from a file, I would suggest the string array or the cell array, as they can deal with different length lines. For backwards compatibility, use a cell array. You may find cellfun relevant for operating on cell arrays. For native string operations, use a string array.
I have created my own version of AES (baby version) everything is working correctly however.
Some binary numbers somehow pick up a 'b' within them example: b1b10101
I am not very clued up on how python works with binary conversions but when trying to convert to a decimal using: pepee = int(pepe,2). It throws the error mentioned in the title when the string contains 'b'.
I found one other answer for this error on here, however the solution does not work for me. using 'format(pepe,'b')' throws an error for me.
I suspect it was written for Python 2.
I need to know, how I can prevent these b's from occurring in my binary strings, or how I can convert them back to the original bit value.
Sample code:
subList2 = ['b1', 'b1', '00', '00']
subStr = b1b10000
subStr = ''.join(subList2)
subDec = int(subStr,2)
Please note I did not intend these b's to appear in the string, they appear during runtime
Have you tried making a smale code snippet to just convert a binary string? Where do you get the binary strings from? If you for example make binary string using bin(), the string will contain a 'b' character.
print(bin(10))
# Outputs: 0b1010
But if you use format(int, 'b') instead, it will not contain the 'b'.
# Set test to a binary string and print it
test = '101001'
print(test)
# Convert test from binary string to int and print it
test = int(test, 2)
print(test)
# Convert test from int to binary string and print it
test = format(test, 'b')
print(test)
Ok,
I got it working.
I had made an athematic error in my code, that was producing minus numbers for binary conversion. which created these 'b' characters in place of the minus numbers. now it is fixed.
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]