Function [pval, t, df] = t_test_2 (x, y, alt): Two samples T-test with unknown equal variances

[xingdan_li]

Dear Sir or Madam,

I am going to use Octave function, [pval,
t, df] = t_test_2 (x, y, alt), to analyze how many sample size needed for
the T-test to satisfy the confidence level of 80% and power level of 70%.
I tried to find answer from online help, but seems from online the function
only back to p-value. 

I have had the two criteria of confidence
and power determined and want to know how many sample size necessary.

Thank you very much for your time and
consideration
 

Sincerely

Xingdan Li