convert a numbere from integer to double
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Hi,
does anyone know how can I covert 1 in 1.0000, please?
Thank you!
4 Kommentare
James Tursa
am 20 Mär. 2015
So, the real problem isn't conversion ... the real problem is that you need to write a text file in a specific format? That was not mentioned at all in your original post. Please tell us the size and type of the variable(s) involved, and the exact text format you want in the file.
Andrew Gerlach
am 29 Sep. 2020
Most of the time Matlab handles this fine, but there are cases when you need to explicitly convert a number type. For example, I just loaded imaging data from a .nii file. When I tried to get the standard deviation from a time series, I got the following error:
>> std(ts)
Error using var (line 74)
Invalid data type. First input argument must be single or double.
Error in std (line 59)
y = sqrt(var(varargin{:}));
The fix was to convert to double manually:
>> std(double(ts))
ans =
128.1063
Antworten (3)
James Tursa
am 18 Mär. 2015
Bearbeitet: James Tursa
am 18 Mär. 2015
Your question is not clear. If the number is a scalar double and exactly 1, it will display as 1 without the trailing 0's. If it is very close to 1 but not exactly 1, it will display with 0's. E.g.,
>> 1
ans =
1
>> 1+eps(1)
ans =
1.0000
To get more digits to display you can use format. E.g.,
>> format long
>> 1
ans =
1
>> 1+eps(1)
ans =
1.000000000000000
If you really have an integer type and need to convert it to double type, use the double function. E.g.,
>> k = int32(1)
k =
1
>> class(k)
ans =
int32
>> d = double(k)
d =
1
>> class(d)
ans =
double
Stephen23
am 20 Mär. 2015
Bearbeitet: Stephen23
am 20 Mär. 2015
Here is one easy way that you can save a vector of values with your chosen precision: with dlmwrite:
>> A = [-1, 1, 1, -1];
>> dlmwrite('temp.txt',A, 'precision','%.4f');
produces me a file which includes this text:
-1.0000,1.0000,1.0000,-1.0000
4 Kommentare
Stephen23
am 23 Mär. 2015
Bearbeitet: Stephen23
am 23 Mär. 2015
If you want to control the spaces individually then you will need to use a lower-level function, such as fprintf:
>> A = [-1, 1, 1, -1];
>> fid = fopen('temp.txt','wt');
>> fprintf(fid,' %.4f,%.4f\n',A);
>> fclose(fid);
gives me a file with this inside (there is a space in front of the first column):
-1.0000,1.0000
1.0000,-1.0000
Note that fprintf will simply keep applying that formatting to the input variables until it runs out of variable... and this is columnwise! You might need to transpose the data before inputting it into fprintf.
If this does not resolve your formatting issues, please upload an example file with the exact formatting that you need, and I will show you how to generate it using dlmwrite or fprintf.
Shantanu Jana
am 23 Mär. 2015
Bearbeitet: Shantanu Jana
am 23 Mär. 2015
you can do this process and latter use 'ans' as variable that hold your answer
>> a=1
a =
1
>>a = double(a)
>> sprintf('%0.4f', a)
ans =
1.0000
>>
2 Kommentare
Guillaume
am 23 Mär. 2015
>>a = 1
creates a of type double. Therefore:
>>a = double(a)
does nothing whatsoever.
Stephen23
am 23 Mär. 2015
Bearbeitet: Stephen23
am 23 Mär. 2015
Lets try the suggested code:
>> a = 1;
>> class(a)
ans = double
Lo! we already have a double! Which means that the code suggested by Shantanu Jana:
>> a = double(a);
does nothing useful at all, as a is already of class double.
MATLAB's documentation about floating point numbers states that "...The default is double precision...". My first comment to the original question also clarifies this.
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