Custom fprintf output formatting.

I'm currently trying to build a function that will enable myself to have an output in Engineering Notation within fprintf. The following script is supposed to resolve a 3D force vector into it's i/j/k format in Eng Notation.

function [] = ABGresolve(force,alpha,beta,gamma)
Fx = force*cosd(alpha); % i
Fy = force*cosd(beta) ; % j
Fz = force*cosd(gamma); % k
val = [Fx Fy Fz]    ;% Force vector
% convert exponent to *10^(3(orderOfMag))
% so that, for instance, x^4 would be 10^3(1)
tempVal = abs(val)  ;% removes negatives for log10
orderOfMag=floor(log10(tempVal)./3);
if val == 0
 orderOfMag = 3  ;% can't log a value of 0, so....
end
%Here you can change the number of digits to the left
% of the decimal. fiddle to understand it.
offset=0-orderOfMag;
% Divides original value by
% power of 3n to get value between 1-1000
valueToPrint=val./(10.^(3.*orderOfMag));
valueToPrint = val.*10.^offset; % % Old stuff I don't use
precision = 4       ;% number of display digits
expPrecision = 3    ;% number of digits in the exponent
if orderOfMag > 0
  formatStr = ['%0' num2str(expPrecision) 'i'];
else
  formatStr = ['-%0' num2str(expPrecision) 'i'];
end
value = num2str(valueToPrint,precision);
exponent = [formatStr,abs((orderOfMag).*3)];
your_string = [ value(1:6),  'e', sprintf(formatStr,exponent(:)) ...
      value(2),'e', sprintf(formatStr,exponent(:)) ...
      value(3),'e', sprintf(formatStr,exponent(:))]
fprintf('F ={ %.4ei   %.4ej   %.4ek}\n',Fx,Fy,Fz);
end

When I try to format the components, I get a bunch of gibberish in the output. I need to convert my character string to a [1x3] or a [3x1] array and somehow get the exponent to work as a multiple of 3. This is my current output:

86.6  e-6e-.e-

I was trying to adapt this Answer on a very similar question to do multiple elements withing a single vector ( Val = [Fx Fy Fx] ) however I don't know where my errors are.

I started learning how to use the R2010a version of MATLAB only a couple weeks ago in my Programming class, so my understanding is rather limited in regards to the built in functions.

Thanks in advance.

Edit: Updating my function in regards to Walter's realization that I was double-formatting a string.

[dpb]

What's the specific problem encountered?

[Kris Glasier]

Yes... I did forget to mention that. I'll update the OP, but when I try to format the components, I get a bunch of gibberish in the output. I believe it's the binary equivalent of the character strings. This is what I get in the output:

8e-045-037-048-051-105-000-000-0006e-045-037-048-051-105-000-000-000.e-045-037-048-051-105-000-000-000

[per isakson]

• Keep it simple!
• See Debug a MATLAB Program

and

K>> class(value)
ans =
char
K>> formatStr
formatStr =
-%03i
K>> class( exponent )
ans =
char
K>> sprintf(formatStr,exponent(:))
ans =
-045-037-048-051-105-003-003-003

What should the output look like?

[Kris Glasier]

I'm trying to get the output to give my format in Engineering notation through fprintf. In this case, I'm looking to get it to give Fx, Fy, and Fz as

F = {1.234e567j 12.34e567i 123.4e567k}

Where 567 is a multiple of 3, for the exponent. and the decimal floats to make a value between 1-1000. If you don't know CVN, the i,j, and k represent the x, y, and z components in a 3D Cartesian grid. Essentially I want it to look like the fprintf I have at the end of the function, but instead of it formatting with %.4e, since that gives me a 1.234e5 response, or a value between 1-10 with an exponent n, rather than 3n, if that makes any sense.

All of the individual components work, but being as I put the values in as a character string, all the inputs are in one cell and I can't seem to find a way to tie them all together.

Answer 1

[Walter Roberson]

You use sprintf(formatStr,exponent(:)) after having done

exponent = [formatStr,abs((orderOfMag).*3)];

so your exponent() array starts with your formatStr and that is being converted using your format string.

[Kris Glasier]

Ah, that did clear a lot of the mess up, Walter. Thank you! However I realize now I have a problem with my values being a string (and only being stored in a 1x1 array). So now my feed, if I put value(1) I simply get the first character (8). Or if I put value(1:5) I get the whole 1.234 value. But if a negative is inserted (ie, an alpha/beta/gamma of >90) the whole set slides over.

Is there a way to turn that 30 odd character string (5-6 characters + 6 spaces between each number set) into a 1x3 or 3x1 array?