Make num2str in engineering format

Hey, I'm writing this code:

disp(['Cutoff frequency: ',num2str(wcutoff,'%e')]);

and this displays the frequency in an normal exponential format, but I want it to be in eng format. This means that instead of:

5.2e10

I want it to show:

52.0e9

Is that possible? A possible workaround could be to use "format shortEng" and than separate the display code into 2 lines, but than I need to find a way that it'll display it in one output line or something like that...

Answer 1

[Yoav Romach]

Ok, I've actually came up with a better, simpler solution:

format shortEng
disp([' Cutoff frequency: ', strtrim(evalc('disp(wcutoff)'))]);

strtrim is needed because the evalc returns numerous leading and trailing white space, but this produces exactly the output I wanted, without the helper function.

[Yoav Romach]

I know it's a bit weird choosing my own answer, but is it possible? Could be useful for other users to see this solution!

[Star Strider]

They'll see it anyway.

I came up with my function because I got the impression from your original post that you’d already tried the format shortEng idea and it didn’t produce the result you wanted.

If you want to revert to whatever you had before you invoked format shortEng, (perhaps format shortE), you have to follow the statements you posted with format shortE. It will stay format shortEng until you change it. With the function I wrote, you don't have to change it at all. Just use sprintf with its output.

You can accept your own Answer, but you don’t get any Reputation Points for it. You cannot vote for your own answer. You can’t un-accept an answer you have already accepted.

[Yoav Romach]

Haa, I see, Don't care about the credit though.

My original problem with "format shortEng" was that it didn't work :) I had to push another "evalc('disp(wcutoff)')" inside, and I only thought of that today.

Thanks a lot anyway!

[Star Strider]

My pleasure!

Answer 2

[Steven Lord]

If you're using release R2021a or later I would use formattedDisplayText instead of evalc.

wcutoff = 5.2e10;
t = formattedDisplayText(wcutoff, 'NumericFormat', 'shortEng')

t = 
    "    52.0000e+009
     "

Answer 3

[Harry Dymond]

For the benifit of those stumbling across this old thread in search of answers: my FEX submission num2eng will do what the OP is asking for.

Answer 4

[Jos (10584)]

A similar effect can be obtained by manipulating the string rather than the numbers

X = 52346574 ; 
s1 = sprintf('%.2e',X)
v = sscanf(s1,'%d.%de%d')
s2 = sprintf('%d%.1fe%02d',v(1), v(2)/10, v(3)-1)
disp(['Cutoff frequency: ', s2]);

Which can be made into a function handle:

Val2EngString = @(X) sprintf('%d%.1fe%02d',[1 .1 1] .* sscanf(sprintf('%.2e',X),'%d.%de%d').' - [0 0 1])
disp(Val2EngString(2340000000))

[Star Strider]

I never considered that approach. I’ll take a look at it.