MATLAB中的科学计数法

Question

Say I have an array that contains the following elements: 1.0e+14 * 1.3325 1.6485 2.0402 1.0485 1.2027 2.0615 1.7432 1.9709 1.4807 0.9012

Now, is there a way to grab 1.0e+14 * (base and exponent) individually? If I do arr(10) , then this will return 9.0120e+13 instead of 0.9012e+14 .

Assuming the question is to grab any elements in the array with coefficient less than one. Is there a way to obtain 1.0e+14 , so that I could just do arr(i) < 1.0e+14 ?

Answer 1

I assume you want string output.

Let a denote the input numeric array. You can do it this way, if you don't mind using evalc (a variant of eval , which is considered bad practice):

s = evalc('disp(a)');
s = regexp(s, '[\de+-\.]+', 'match');

This produces a cell array with the desired strings.

Example:

>> a = [1.2e-5 3.4e-6]
a =
   1.0e-04 *
    0.1200    0.0340
>> s = evalc('disp(a)');
>> s = regexp(s, '[\de+-\.]+', 'match')
s = 
    '1.0e-04'    '0.1200'    '0.0340'

Answer 2

Here is the original answer from Alain.

Basic math can tell you that:

floor(log10(N))

The log base 10 of a number tells you approximately how many digits before the decimal are in that number.

For instance, 99987123459823754 is 9.998E+016

log10(99987123459823754) is 16.9999441, the floor of which is 16 - which can basically tell you "the exponent in scientific notation is 16, very close to being 17".

Now you have the exponent of the scientific notation. This should allow you to get to whatever your goal is ;-).

And depending on what you want to do with your exponent and the number, you could also define your own method. An example is described in this thread.