Problems of convert decimal number to a string

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zongxian
zongxian 2020-6-28
评论： Walter Roberson 2021-10-8
Now I want to convert a input decimal number (maybe a input number, not known) to a string, I try to use num2str and string function, but there are some problems that I can not solve.
num = [110.00001, 10.00000000000000001,99.01]';
% I want to num become ["110.00001", "10.00000000000000001","99.01"]
num2str([110.00001, 10.00000000000000001,99.01])
By use num2str it will delete some decimal places, I don't know how to do it, holp someone would help me.

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回答（3 个）

madhan ravi
madhan ravi 2020-6-28
You cannot do that.
Ajay Kumar
Ajay Kumar 2020-6-28
You can define precision property in num2str. For example:
num = [110.00001, 10.00000000000000001,99.01]';
your_ans = num2str(num,10);
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zongxian
zongxian 2020-6-28
编辑：zongxian 2020-6-28
I have an idea, if we set the decimal number as num2str(10.0000000001, '%10.20f'), and then delete the zeros one by one (from the last one digits), until the non-zeros digit, now I have try it, it show '10.00000000010000000827', why the last digits are not zeros??
Walter Roberson
Walter Roberson 2020-6-28
The exact value stored for 10.0000000001 is
10.0000000001000000082740370999090373516082763671875
Values down to 10.000000000000001 can be distinguished from 10.0
10.0000000000000017763568394002504646778106689453125
It is important to remember for this purpose that double() does not use decimal representation: it uses IEEE 754 Double Precision Binary representation, which is a 64 bit representation with 1 sign bit, 11 exponent bits, and 52 explicit fraction bits, plus one "hidden" fraction bit (it is hidden in the exponent in a way.)

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KSSV
KSSV 2020-6-28
编辑：KSSV 2020-6-28
iwant = sprintf("0.12f 0.12f 0.12f",num) ;
Try with sprintf.
You can split each number into a cell using num2cell, and use cellfun with sprintf. Or run a loop for each num.
  1 个评论
zongxian
zongxian 2020-6-28
This way need give the format of the number, but if we don't know the detail decimal number (i.e. '0.12f') will return wrong answer.

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