So say I have three files $(A, B,C)$ that are filled with words.
Say for a specific word $W_{i i}$ want to determine the probability of the word given a file. that is
Calculate: $$ P(W_i|\text{File})$$ so for example say we wanted to determine (for file A) $$P(W_i|A)$$
There are two ways I've seen this which is the correct calculation?
$$P(W_i|A)=\frac{\text{Number Of Times }W_i\text{ Occurs In File }A}{\text{Number Of Words In File }A} $$ If you didnt get that: Count up the number of times W exists in file A then divide it by the number of words in A.
$$P(W_i|A)=\frac{\text{Number Of Times }W_i\text{ Occurs In File }A}{\text{Sum of the Number Of Times }W_i\text{ Occurs In File }A, B, C} $$
Count up the number of times W exists in file $A$ then divide it by the number of times $A$ occurs (number of times $W$ exists in $A$ plus number of times $W$ exits in $B$ .... etc)