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

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Riyadh Muttaleb on 10 Sep 2018
Commented: Steven Lord on 19 Apr 2022
Hi everyone,
I would like to change the number of digits before the decimal point, for example 1.45237E+6 to 145.237E+4

Stephen23 on 10 Sep 2018
Edited: Stephen23 on 11 Sep 2018
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'
Steven Lord on 19 Apr 2022
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