how can I change the number of digits before decimal point?

Hi everyone,

I would like to change the number of digits before the decimal point, for example 1.45237E+6 to 145.237E+4

Thanks in advance,

Riyadh

Answer 1

[Stephen23]

Hmm, interesting problem. Here is one solution that lets you specify how many leading digits you want before the decimal point, before converting to char vector/string:

>> N = 1.45237E+6;
>> D = 3; % digits before decimal point
>> T = 6; % total digits
>> K = 10^(2-D+floor(log10(N)));
>> sprintf('%d%.*e',fix(N/K),T-D,mod(N,K))
ans = '145.237e+04'

Try it with more digits:

>> D = 5;
>> T = 6;
>> K = 10^(2-D+floor(log10(N)));
>> sprintf('%d%.*e',fix(N/K),T-D,mod(N,K))
ans = '14523.7e+02'

[Riyadh Muttaleb]

Thank you so much!

[Riyadh Muttaleb]

just more question how can do that if I have matric (3x5)?

[Stephen23]

"just more question how can do that if I have matric (3x5)?"

Perhaps like this, where A is your array (untested, but should get you started):

C = cell(size(A));
for k = 1:numel(A)
    C{k} = ... convert to char ... A(k);
end
C = C.';
F = [repmat('\t%s',1,size(A,2)),'\n'];
fprintf(F(3:end),C{:})

I recommend that you put the numeric-to-char conversion code inside a function, to give space for the various special cases that you will need to check and probably add into the code (e.g. N=0, N<0, N=Inf, N=NaN, D<=1, D>=T, ...)

[Noah Hovde]

How about expressing the number 0.21e-6 just as it is? I tried using your code and it converts it to 02.10e-07. I really want it to stay as 0.21e-6 so as to preserve units in the calculation that I am performing. Thanks for your help!

[Steven Lord]

If you want the exponent to be a multiple of 3, use one of the ENG options for the format function.

x = 0.21e-6

x = 2.1000e-07

y = 0.21e-7

y = 2.1000e-08

format shorteng
disp([x; y])

   210.0000e-009
    21.0000e-009

format longeng
disp([x; y])

    210.000000000000e-009
    21.0000000000000e-009