Info

此问题已关闭。 请重新打开它进行编辑或回答。

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

1 次查看（过去 30 天）
Muhammed Yusuf Aksel
关闭： MATLAB Answer Bot 2021-8-20
I've tried str2double("26/7"), however it gave NaN as output.
Thanks in advance.

请先登录，再回答此问题。

回答（3 个）

Stephen23
Stephen23 2020-4-4
编辑：Stephen23 2020-4-4
>> 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
John D'Errico
John D'Errico 2020-4-4
编辑：John D'Errico 2020-4-4
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. ;-)
  6 个评论
显示 4更早的评论
John D'Errico
John D'Errico 2020-4-4
编辑：John D'Errico 2020-4-4
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
Stephen23 2020-4-4
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
KALYAN ACHARJYA
KALYAN ACHARJYA 2020-4-4
编辑：KALYAN ACHARJYA 2020-4-4
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
  1 个评论
Muhammed Yusuf Aksel
Muhammed Yusuf Aksel 2020-4-4
So, isn't there any way to evaluate the value of "22/7" first and then store as a double?

标签

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by