Displaying exponential notation with num2str?

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Michael
Michael 2022-8-24
回答： Steven Lord 2022-8-24
I have a value that I want to display within a textbox in a figure. The value hoewer needs to be in exponential notation.
Example:
lambda = 2.4321;
vD = 3.2e5;
fighandle = figure(1);
fighandle.Color = [1,1,1];
fighandle.Position = [10,50,600,400];
fighandle.Name = 'Test';
xlabel('t [min]','FontSize',12,'Interpreter','latex');
ylabel('Temperatur [$^\circ$C]','FontSize',12,'Interpreter','latex');
annotation('textbox', [0.66, 0.15, 0.1, 0.1], ...
'String', {['$\lambda$ = ' num2str(round(lambda,3),'%.3f') ' W/mK'], ...
['$v_D$ = ' num2str(round(vD,1),'%.1f') ' m/s']}, ...
'BackgroundColor', 'White', ...
'Interpreter','latex');
The result looks like this:
But i want the variable b to look like this:
Any ideas? Thank you very much for the help!

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采纳的回答

Star Strider
Star Strider 2022-8-24
Ran in:
I wrote a little utility program to do that sort of thing a few years ago.
Try this —
Q1 = [-pi*1000; 0; pi*100];
expstr = @(x) [x(:).*10.^ceil(-log10(abs(x(:)+(x==0)))) floor(log10(abs(x(:)+(x==0))))]; % Updated: 2021 05 04
Result = sprintf('%+.4fe%+04d\n', expstr(Q1).')
Result =
'-3.1416e+003 +0.0000e+000 +3.1416e+002 '
V = expstr(Q1)
V = 3×2
-3.1416 3.0000 0 0 3.1416 2.0000
Create the sprintf format string (that I use here) to give the result you want.
.
  2 个评论
Michael
Michael 2022-8-24
编辑：Michael 2022-8-24
Thank you very much! That did, what I was looking for :)
I implemented it this way within the annotation textbox:
vD_expstr = expstr(vD);
% ...
['$v_D$ = ' num2str(round(vD_expstr(1),1),'%.1f') ' $\cdot$ 10' num2str(vD_expstr(2),'$^{%.0f}$') ' m/s']
Star Strider
Star Strider 2022-8-24
As always, my pleasure!
That will work, since num2str allows format strings, although sprintf might be an easier way to implement it.
I created ‘expstr’ precisely for the purpose you’re using it!

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更多回答（1 个）

Steven Lord
Steven Lord 2022-8-24
Ran in:
Another function that might be of interest to you is formattedDisplayText, if you want to capture how the variable would be displayed in MATLAB using a certain display format.
x = pi
x = 3.1416
y1 = formattedDisplayText(x)
y1 =
" 3.1416 "
format longeng
x
x =
3.14159265358979e+000
y2 = formattedDisplayText(x)
y2 =
" 3.14159265358979e+000 "

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