How to use fprintf function?

I have to print the values of f(x) = sin(x^3) at the points x = 5.201, −8323.6, 0.0003 in floating point (f format) with 8 digits after the decimal and in scientific notation (e format) with 10 digits after the decimal.

Any help at all would be appreciated. I have no clue how to do this.

Answer 1

[Star Strider]

The fprintf function optionally requires a ‘fileID’ variable as its first argument, with 1 indicating ‘stdout’, that being the Command Window. Otherwise it will be to the file you want to write to. (I used it in the first fprintf call but not in the second.)

To print the values of ‘x’ and f(x), this works:

x = [5.201, -8323.6, 0.0003];
f = @(x) sin(x.^3);

fprintf(1, 'f(%f) = %.8f\n', [x; f(x)])
fprintf('f(%f) = %.10e\n', [x; f(x)])

f(5.201000) = 0.63076123
f(-8323.600000) = -0.52794696
f(0.000300) = 0.00000000

f(5.201000) = 6.3076122538e-01
f(-8323.600000) = -5.2794696417e-01
f(0.000300) = 2.7000000000e-11

The (\n) is a newline character.

[Kaylene Widdoes]

Awesome! Thank you so much! Any chance you know this one as well? http://www.mathworks.com/matlabcentral/answers/242146-function-file-question

[Star Strider]

My pleasure!

Here on MATLAB Answers, if a particular Answer solves your problem, please Accept it.

I looked at your other Question. I don’t understand what x^(+) means, so I’ll wait for you to clarify that.

[Kaylene Widdoes]

This was all I was given. Thanks!

[Star Strider]

As always, my pleasure!

I posted a Comment to your Question there, rather than an Answer. I don’t understand the Question well enough to be able to provide an Answer.

Answer 2

[Stephen23]

This should get you started:

>> x = [5.201,-8323.6,0.0003];
>> sprintf(' %.8f',x)
ans =  5.20100000 -8323.60000000 0.00030000
>> sprintf(' %.10e',x)
ans =  5.2010000000e+000 -8.3236000000e+003 3.0000000000e-004

MATLAB has very readable and accessible documentation complete with working examples for you to try out. This is the best place to find out how to do things and how to use functions. You were told what function to use, the next step is to read its documentation and try some of its examples. Then you can see how these can be adapted to your needs, try some small changes... keep on going until you have figured out the problem. Note you should not try to solve any code problem by sitting down writing code! The most important steps are to first understand the problem and then to understand what tools you have to help you, only then comes writing some code...

Here is the fprintf documentation:

http://www.mathworks.com/help/matlab/ref/fprintf.html

I would also highly recommend that you do these tutorials, which are an excellent introduction to MATLAB:

http://www.mathworks.com/help/matlab/getting-started-with-matlab.html

[Kaylene Widdoes]

I'm getting a parse error with 0.0030000?

[Steven Lord]

Don't copy and paste the lines that start with "ans =". Those are the output from the commands on the previous lines (the lines that start with ">>".)

[Kaylene Widdoes]

So the next step would be to write the sin function correct? So wouldn't it be easiest if I defined a function y=(sin(x^3)) and then did the same sprintf code with y(x) rather than x?

[Kaylene Widdoes]

Any chance you can give me a start on this problem as well? http://www.mathworks.com/matlabcentral/answers/242146-function-file-question

Answer 3

[Gayan]

X=(5-19/7+2.5^3)^2

X = 320.7937

[Walter Roberson]

I do not understand how this answer helps people use fprintf() ?