How to convert string "26/7" into a double variable?

I've tried str2double("26/7"), however it gave NaN as output.

Thanks in advance.

Answer 1

[Stephen23]

>> str = '26/7';
>> vec = sscanf(str,'%f/%f');
>> vec(1)./vec(2)
ans =  3.7143

One line (but I would not recommend using this):

>> prod(sscanf(str,'%f/%f').^[1;-1])
ans =  3.7143

[Muhammed Yusuf Aksel]

Nice! thanks.

Answer 2

[John D'Errico]

Whilst I am one of the people who tends to equate eval with evil...

str = '22/7';
eval(str)
ans =
          3.14285714285714

Sometimes it can come to the rescue. Eval has a Dr. Jekyll and Mr Hyde thing about it though, so beware the dark side. ;-)

[Muhammed Yusuf Aksel]

I am glad I know about Dr Jekyll and Mr Hyde :) Otherwise it would be a huge what the heck moment :D

Thanks for the answer, I didn't know MATLAB had an eval() function.

[Guillaume]

Note that str2num would be slightly safer. It is just a wrapper for eval so has the same issues but, at least, it tries to protect you from the most obvious dangers:

>> str2num('22/7')
ans =
          3.14285714285714

[Muhammed Yusuf Aksel]

@Guillaume cool, this outputs a double, right?

[Guillaume]

Yes

[John D'Errico]

Yes. str2num is an option too. But then I could not have called it evil quite as easily. :)

And yes, the Jekyll and Hyde remark was something I wondered if others would catch.

https://en.wikipedia.org/wiki/Strange_Case_of_Dr_Jekyll_and_Mr_Hyde

Not unlike putting a reference to a slide rule in an answer these days. Most people today would look at a slide rule with a blank stare, wondering what anyone would do with it.

https://en.wikipedia.org/wiki/Slide_rule

I did cherish my slide rule. They are mainly relegated to the antique shops now, in a sense a loss. :{

[Stephen23]

As well as being insecure eval is also slower than sscanf and rdivide, e.g. 1e5 iterations:

Elapsed time is 1.088572 seconds. % SSCAF and RDIVIDE
Elapsed time is 5.502366 seconds. % evil EVAL

Answer 3

[KALYAN ACHARJYA]

X = str2double(str) converts the text in str to double precision values.

Text is "22/7" This is not a number right "/" . What do you expect at the output?

Same case:

>> X = str2double('22+7')
X =
   NaN

But if we add then

>> X = str2double('29')
X =
    29

[Muhammed Yusuf Aksel]

So, isn't there any way to evaluate the value of "22/7" first and then store as a double?