convert milliseconds (ms) to seconds (s)

Hello,

we have an array with stimuli onset times in milliseconds,

ms = [1600901     1970185     2340488     2710467     3080481     3449869]

and we want to convert those values to seconds with a specific format, that would be, 1600901/1000 = 1600.901.

But when I do that in MATLAB I get this result:

s = ms/1000

s = 

   1.0e+03 *

    1.6009    1.9702    2.3405    2.7105    3.0805    3.4499

Is there a way to obtain this insead:

s = [1600.901     1970.185     2340.488     2710.467     3080.481     3449.869]

Thank you

Answer 1

[Stephen23]

You can change the format of how numbers are displayed, e.g. "shortG"

>> format shortG
>> ms/1000
ans =
       1600.9       1970.2       2340.5       2710.5       3080.5       3449.9

Or "longG":

>> format longG
>> ms/1000
ans =
                  1600.901                  1970.185                  2340.488                  2710.467                  3080.481                  3449.869

The default is "short":

>> format short
>> ms/1000
ans =
   1.0e+03 *
    1.6009    1.9702    2.3405    2.7105    3.0805    3.4499

Note that none of these make any difference to the numeric values stored in your array. Do not confuse how numbers are displayed with what values are stored in a variable. These are two quite different things.

[looking for answers]

Hi Stephen,

Thank you for your response.

I would like to change the way the values are stored. That means if I open the "s" array from the workspace I want to see 1600.901 and not 1.0e+03 * 1.6009.

That's what I am trying to do.

[Stephen23]

"I would like to change the way the values are stored. That means if I open the "s" array from the workspace I want to see 1600.901 and not 1.0e+03 * 1.6009."

Numeric data classes do not store any format information.

You can change the format for the Command Window and for the Variable Viewer and anything else that has a customizable display format, but using standard binary floating point numbers what you ask for is impossible because they do NOT store any formatting information whatsoever.

[Guillaume]

You are indeed confusing the ways the number are stored and display.

Matlab store 1600.901 neither as 1600.901 or 1e3 * 1.6009. The way it is stored is actually irrelevant but it is stored as a binary fraction (1.1001000000111001101010011111101111100111011011001001b * 2 ^ 10, resolving to ~= 1.5633798828125 * 2^10) and there's nothing you can change about that. The actual decimal value stored in memory is 1600.9010000000000673026079312.

You are asking to change the way matlab displays the number to you, and for that you should use format shortg or format longg as answered by Stephen.

[looking for answers]

Hi Guillaume and Stephen,

Thank you both for your asnwer and for taking the time to explain in such a clear way how floating numbers are displayed/stored.

Answer 2

[madhan ravi]

format longg
ms / 1000
doc format 

[looking for answers]

Hi madhan,

Thank you for your response but I think what you are suggesting changes the way the numbers are displayed and not the way they are stored.

[madhan ravi]

See Stephen‘s valuable comment - https://in.mathworks.com/matlabcentral/answers/473594-convert-milliseconds-ms-to-seconds-s#comment_728675

[looking for answers]

Thank you madhan for your answer.