Plot title sprintf format pi

How can I display on a plot's Title the input value pi with Greek character "π" or in English "pi". For example: prompt = 'What is the original value? '; x = input(prompt) I insert the value pi/2 So i want the plot title to be like: Output=π/2 I used the following code but it keeps giving me the value 0.707 instead of the π/2 or pi/2 i want.

str = sprintf('Output  x=%d',x);
title(str);

Answer 1

[Kirby Fears]

x is a double-precision floating point number. It will be displayed as a decimal by default. You can control how the double is represented (like scientific notation), but there is no built-in ability to display a double in terms of pi multiples. You're specifically trying to represent x in terms of pi/n for the appropriate n value.

Use the '\pi' character to display the symbol for pi. Calculate the value n = pi/x to build the expression "x = pi/n" in the title.

str = sprintf('Output  x=%s/%d','\pi',pi/x);
title(str);

[Nick Papanikolaou]

Thank you very much.But it seems it can't display correct the x=3Π/4 value. It gives π/1

Am I doing something wrong?

[Kirby Fears]

Here's another approach using rats() to generate a rational approximation of the fraction of pi:

x = pi * 3/4;
R = strtrim(rats(x/pi));
str = sprintf('Output  x=%s*%s','\pi',R);
% plot(...);
title(str);

[Kirby Fears]

To make it look really nice, you'll need a bit of case handling to insert \pi into the proper position.

x = pi * 3/4;
R = strtrim(rats(x/pi));
idxFrac = strfind(R,'/');
if isempty(idxFrac),
    if strcmp(R,'0'),
        fracStr = '0';
    elseif strcmp(R,'1'),
        fracStr = '\pi';
    elseif strcmp(R,'-1'),
        fracStr = '-\pi';
    else
        fracStr = [R,'\pi'];
    end
else
    leftStr = R(1:idxFrac-1);
    rightStr = R(idxFrac:end);
    if strcmp(leftStr,'1'),
        fracStr = ['\pi' rightStr];
    elseif strcmp(leftStr,'-1'),
        fracStr = ['-\pi' rightStr];
    else
        fracStr = [leftStr '\pi' rightStr];
    end
end
titleStr = sprintf('Output  x = %s',fracStr);
% plot(...);
title(titleStr);

[DEBARSHI MAJUMDER]

thanks@Kirby Fears