How can I use the ( nchoosek ) for the following case :- nchoosek(80,64) ???

I get the following warning message:

Warning: Result may not be exact. Coefficient is greater than 9.007199e+15 and is

only accurate to 15 digits.

Answer 1

[Walter Roberson]

nchoosek(sym(80),64)
nchoosek(uint64(80),64)

result is 26958221130508525 which is 17 digits

I didn't expect uint64 to work but it does for this case

[Torsten]

The "usual" way:

format long
exp(sum(log(65:80))-sum(log(1:16)))

ans = 
     2.695822113050849e+16

[Walter Roberson]

exp() gives an approximation when you get to that kind of range, and it is worse than eps() of the range.

format long g
nchoosek(sym(80),64) - exp(sum(log(65:80))-sum(log(1:16)))

ans = 

33

eps(nchoosek((80),64))

Warning: Result may not be exact. Coefficient has a maximum relative error of 2.2204e-16, corresponding to absolute error 6.

ans = 
     4

[Steven Lord]

I didn't expect uint64 to work but it does for this case

We're clever :)

[hayder fadhil]

sorry sir

I have the following

x=[1:1:26]
y=16;
C = nchoosek(x,y)

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

and I need to find the same process for

x=[1:1:80]
y=64;

How can i find C

[Walter Roberson]

x = 64:80;
y = 64;
C = arrayfun(@(X) nchoosek(uint64(X), y), x.')

C = 17×1

1 65 2145 47905 814385 11238513 131115985 1329890705 11969016345 97082021465