What is wrong with my fprintf?

I am trying to print out the value of y to be 6 decimals, if I type it as format long or short it pops out those lengths. I am trying to make as many decimals places as D, but the default is 6 if not declared.

function y=atan_approx(x,D)
y=0;
n=1;
k=1;
if nargin==1,D=6,disp('Value of D was set to 6'), end
while n<100
  y=y+(x.^n./n).*k;
  n=n+2;
  k=k*-1;
end
fprintf('The value of the approximation is %10.Df\n',y)
z=-1:0.01:1;
plot(z, atan(z),'--g')
hold
plot(x,y,'ro')
end
>>format long
>>atan_approx(0.5,7)
The value of the approximation is current plot held
ans = 
0.4636476090086

if i make it format short the ans is 0.4636

Answer 1

[Walter Roberson]

fprintf('The value of the approximation is %10.6f\n',y)

Your %10.Df uses an invalid format specifier, 'D', so that ends printing out on that line. Then the "current plot held" is coming from the "hold" command you have.

Answer 2

[per isakson]

"What is wrong with my fprintf?" &nbsp I assume that you intend to control the number of decimals places with the variable D. Here are two format specifiers, which do that. (Look up the help on fprintf. )

>> cssm( pi, 5 )
The value of the approximation is    3.14159
Or with a parameterized specifier    3.14159
>>

where

function  cssm( y, D )
    frmt = sprintf( 'The value of the approximation is %%10.%df\n', D );
    fprintf( frmt, y );
    fprintf( 'Or with a parameterized specifier %10.*f\n', D, y );
end