How do I change string to double without changing number of zero under decimal point?

Question

Capulus_love 2020-8-21

0
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https://ww2.mathworks.cn/matlabcentral/answers/582794-how-do-i-change-string-to-double-without-changing-number-of-zero-under-decimal-point

回答： Walter Roberson 2020-8-21

a = '24.5';aa = "24.5";
b = str2double(aa)
d = double(a)
d = double(aa)
c = cast(aa,'double')
c = cast(a,'double')

i know

class(a)
class(aa)

answer is

ans = 'char'
ans = 'string'

Each answer shows either

24.5000

or

[50 52 46 53]

Question is that how can I change class char to double without changing number of zero under decimal point?

24.5

Is there any function?

2 个评论
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KSSV 2020-8-21

在 MATLAB Online 中打开

24.5000

In the above where is change in decimal point?

Capulus_love 2020-8-21

sorry, i mean the number of zero under the decimal point

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Answer 1

Walter Roberson 2020-8-21

0
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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/582794-how-do-i-change-string-to-double-without-changing-number-of-zero-under-decimal-point#answer_483224

在 MATLAB Online 中打开

You cannot. class double does not keep track of how many trailing decimal points are present. class double is not stored in decimal at all: it is stored in binary floating point using an international standard representation that cannot exactly represent 1/10 (for the same mathematical reasons that decimal cannot exactly represent 1/3)

When you are seeing 2.5000 you are seeing one of the several different ways that the mathematical number can be represented. If you were to command

format long g

and display the number again you would see another representation. format bank would give you another.