How do you cast a double to an integer in R?

Question

My question is: Suppose you have computed an algorithm that gives the number of iterations and you would like to print the number of iterations out. But the output always many d

Answer 1

There are some gotchas in coercing to integer mode. Presumably you have a variety of numbers in some structure. If you are working with a matrix, then the print routine will display all the numbers at the same precision. If you have calculated this result with an arithmetic process it may be actually less than 64 bit display as that value.

> 64.00000000-.00000099999
[1] 64
> 64.00000000-.0000099999
[1] 63.99999

So assuming you want all the values in whatever structure this is part of, to be displayed as integers, the safest would be:

round(64.000000, 0)

... since this could happen, otherwise.

> as.integer(64.00000000-.00000000009)
[1] 63

The other gotcha is that the range of value for integers is considerably less than the range of floating point numbers.