Help with a piece of code

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jip prinsen 2017-9-21

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评论： José-Luis 2017-9-21

Hey all, I'm working on a school project that's about changing the order of characters in a binary array. In the process of writing it, I found a bit of code online to help me:

v = sprintf('%d', array3)
endarray = v - '0'

Basically, what this does is it takes the value of array3, which for example is [1011010] and creates a variable endarray, which in turn becomes [1 0 1 1 0 1 0]. When I implemented this piece of code I didn't quite know how it functioned, and it wasn't explained on the page where I found it, so I decided to go back to it later. Unfortunately I still haven't figured it out. I can't wrap my head around the combinations of sprintf, %d, and the -'0'.

Any help with understanding these two lines would be greatly appreciated.

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Pal Szabo 2017-9-21

I recommend to replace "Help with a piece of code" with something more meaningful

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Answer 1

Pal Szabo 2017-9-21

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编辑：Pal Szabo 2017-9-21

array3 is an integer. Sprintf needs to no that it is in decimal point notation, that's why you need the %d. More info: https://uk.mathworks.com/help/matlab/matlab_prog/formatting-strings.html. Strings in matlab are basically chain of chars. By subtractring -'0', you are basically subtracting 0 (decimal notation) from the ASCII values of the chars within the string. Executing an operation on each char within the chain of chars (aka on the string) gives a result of individual chars, since the operation only valid on individual chars, not on the string as a whole. Try this for example:

 array3 = [1011010]
 v = sprintf('%d', array3)
 endarray = v - '0' - 'd'

You get

-99 -100 -99 -99 -100 -99 -100

as result. 'd' is the ASCII character with decimal value 100. https://en.wikipedia.org/wiki/ASCII

You get the same result if define endarray like this:

endarray = v - '0' - 100

Here 100 is an integer, not a chain of chars.

Sub in different values for 'd': the results are consistent with the ASCII table.

Hope this helps.

EDIT: I see you added a tag 'binary'. I do not think array3 is binary, just because it has only ones and zeros, it is pretty much a decimal value. Just like 8+2=10, 10 is not binary.