What is '-1.#IND'?

Question

I have some code that will allow me to draw a crescent moon shape, and have extracted the values to excel to be drawn. However in place of some numbers, there is -1.#IND in place. Firstly if anyone could explain what this means, as Google came back with 0 links. And secondly if there is anyway to stop it from occurring.

There is a brief analogy of my code. I have lots more code besides this, however that is just calculating angles.

for(int j=0; j<=n; j++)//calculation for angles and output displayed to user
{
    Xnew2 = -j*(Y+R1)/n; //calculate x coordinate
    Ynew2 = Y*(pow(1-(pow((Xnew2/X),2)),0.5));
    if(abs(Ynew2) <= R1)
        cout<<"\n("<<Xnew2<<", "<<Ynew2<<")"<<endl;
}

MORE INFO

I'm now having the problem with this code.

for(int i=0; i<=n; i++) //calculation for angles and output displayed to user
{                                          
    Xnew = -i*(Y+R1)/n; //calculate x coordinate
    Ynew = pow((((Y+R1)*(Y+R1)) - (Xnew*Xnew)), 0.5); //calculate y coordinate

AND

for(int j=0; j<=n; j++)//calculation for angles and output displayed to user
{
    Xnew2 = -j*(Y+R1)/((n)+((0.00001)*(n==0))); //calculate x coordinate
    Ynew2 = Y*(pow(abs(1-(pow((Xnew2/X),2))),0.5));
    if(abs(Ynew2) <= R1)
        cout<<"\n("<<Xnew2<<", "<<Ynew2<<")"<<endl;

I am having the problem drawing the crescent moon that I cannot get the two circles to have the same starting point? If this makes sense, I am trying to get two parts of circles to draw a crescent moon as such that they have the same start and end points. The only user input I have to work by is the radius and chosen center point.

If anyone has any suggestions on how to do this, it would be great, currently all I am getting more a 'half doughnut' shape, due to the circles not being connected.

Answer 1

You are raising a negative number to the power of a non-inverse (i.e. 1/2, 0.5, 0.25, 0.333333, etc.) which results in a complex number. Like sqrt(-1) aka (-1)^(0.5)

Additionally you could also be equating 0/0 in two of your lines of code.

Use this code instead: (It takes the absolute value of your power's base (preventing negative values, thus preventing imaginary answers (complex numbers = NaN = -1.#IND)) It also prevents you from dividing by 0 if n == 0... in this event it adds 0.00001 to the denominator

for(int j=0; j<=n; j++)//calculation for angles and output displayed to user
{
Xnew2 = -j*(Y+R1)/((n)+((0.00001)*(n==0)); //calculate x coordinate
Ynew2 = Y*(pow(abs(1-(pow((Xnew2/X),2))),0.5));
if(abs(Ynew2) <= R1)
cout<<"\n("<<Xnew2<<", "<<Ynew2<<")"<<endl;
}
{
Xnew3 = -j*(Y+R1)/((n)+((0.00001)*(n==0));  //calculate x coordinate
Ynew3 = Y*(pow(abs(1-(pow((Xnew3/X),2))),0.5)); //calculate y coordinate
if(abs(Ynew3) <= R1)
cout<<"\n("<<Xnew3<<", "<<Ynew3<<")"<<endl; //show x,y coordinates
}

*In the future avoid taking roots of negative numbers (which is the same as raising a negative number to a non-inverse-fraction power), avoid taking a logarithm of a negative number, and avoid dividing by 0 these all produce NaN (-1.#IND)

This code may be better (it uses conditional values to make your power's base zero if it is ever less than zero to prevent imaginary answers):

for(int j=0; j<=n; j++)//calculation for angles and output displayed to user
{
Xnew2 = -j*(Y+R1)/((n)+((0.00001)*(n==0)); //calculate x coordinate
Ynew2 = Y*(pow(((1-(pow((Xnew2/X),2)))*((1-(pow((Xnew2/X),2)))>(0))),0.5));
if(abs(Ynew2) <= R1)
cout<<"\n("<<Xnew2<<", "<<Ynew2<<")"<<endl;
}
{
Xnew3 = -j*(Y+R1)/((n)+((0.00001)*(n==0));  //calculate x coordinate
Ynew3 = Y*(pow(((1-(pow((Xnew3/X),2))))*((1-(pow((Xnew3/X),2))))>(0))),0.5)); //calculate y coordinate
if(abs(Ynew3) <= R1)
cout<<"\n("<<Xnew3<<", "<<Ynew3<<")"<<endl; //show x,y coordinates
}

* I'd also like to point out what "Magtheridon96" mentioned in his answer. The code now makes sure n is not equal to zero otherwise you could be dividing by zero, although I think that would produce #INF not #IND... unless "-j(Y+R1)" is also zero, then it will be 0/0 which will be #IND

Answer 2

#IND means an indetermined form.

What you have there is something known as 'Not a number' or NaN for short.

Quoting from Wikipedia, generation is done by:

• Operations with a NaN as at least one operand.
• The divisions 0/0 and ±∞/±∞
• The multiplications 0×±∞ and ±∞×0
• The additions ∞ + (−∞), (−∞) + ∞ and equivalent subtractions
• The square root of a negative number.
• The logarithm of a negative number
• The inverse sine or cosine of a number that is less than −1 or greater than +1.

You're doing at least one of those things.

Edit:

After analyzing your code, these are 2 possibilities:

• When n == 0 in the first iteration where j == 0 too, Xnew2 will be -1.#IND
• When Xnew2 is greater than X, Ynew2 will be complex -> NaN

Answer 3

This from the Wikipedia entry for IEEE 754 Nan:

There are three kinds of operations that can return NaN:

Operations with a NaN as at least one operand.
Indeterminate forms
    The divisions 0/0 and ±∞/±∞
    The multiplications 0×±∞ and ±∞×0
    The additions ∞ + (−∞), (−∞) + ∞ and equivalent subtractions
    The standard has alternative functions for powers:
        The standard pow function and the integer exponent pown function define 00, 1∞, and ∞0 as 1.
        The powr function defines all three indeterminate forms as invalid operations and so returns NaN.

Real operations with complex results, for example:
    The square root of a negative number.
    The logarithm of a negative number
    The inverse sine or cosine of a number that is less than −1 or greater than +1.

Answer 4

You are doing something illegal to a floating point number, such as taking the square root of a negative number. This is presumably on Windows. On Linux, you would get NaN (not a number) or inf. See -1 #IND Question for further information; the link provided in the second answer is helpful.