I cannot print on an output file

[math8]

So I am writing this code that analyzes a file called "analysis.txt" and prints out in an ouput file (called "report.txt") the results of the analysis, i.e.,(the frequency of all alphabet letters present in the file).

I am having trouble with outputing on the file2.

here is what I have:

#include<iostream>
#include<fstream>

using namespace std;
ifstream file1;
void menu0();
void menuA();
void Frequency(char chr, float num, char a[1000]);
char alphabet[27]={'a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','q','r','s','t','u','v','w','x','y','z','\0'};



int main(){
bool done=false;
char filename[40];
int choice;    
char char_to_check; 
char a[1000];
int counter=0;
    
menu0();  

do{
 cout<<"Please give file name: ";
 cin.getline(filename,sizeof(filename));  
 file1.open(filename); //filename is open
 if(file1.fail()){ file1.clear();}
 else {done=true; }
 }while(!done);  
 
 while(file1.eof()==false){
 file1>>a[counter++];}
 a[counter-1]='\0';
 float num=counter-1;
 cout<<"The number of all characters in the file is "<<num<<endl<<endl;
 
 file1.close();

do{
 menuA();
 cout<<"Choose: ";
 cin>>choice;
 
 if(choice==1){
  cout<<"Please give character to check: ";    
  cin>>char_to_check; 
  Frequency(char_to_check, num, a) ;
  }
   
 else if(choice==2){
  cout<<"Report stored in file: report.txt "<<endl;
  ofstream file2("report.txt");
  for(int p=0;p<26;p++){
  file2<<Frequency(alphabet[p], num, a) ;
  file2<<endl;}
  file2.close();  
  }
  
 else cout<<"Not a valid option."<<endl;
 
} while(choice !=0);

cout<<"Now quitting.."<<endl<<endl;
 
//system("PAUSE");
   //pause();
return 0;
}


void menu0(){
  cout<<"This program accepts a text file from a user and performs"<<endl;
  cout<<"an analysis of the letters and characters used by the author."<<endl<<endl;   
}   
void menuA(){
  cout<<"Choose"<<endl;
  cout<<"1. To perform analysis on a single character."<<endl;   
  cout<<"2. To write analysis for all alphabet in a file."<<endl; 
  cout<<"0. To quit."<<endl; 
}  
void Frequency(char chr, float num, char a[1000]){
 float counts_chr=0;
 int k=0;
 float freq;
 for(int j=0;j<num;j++){
    if(a[j]==chr){k++;}  }
    counts_chr=k;
   freq=counts_chr/num;
   cout<<"Character "<<chr<<" appears "<<counts_chr<<" times in the text."<<endl;
   cout<<"It has a frequency of "<<freq <<"."<<endl;}

It's giving me the error: " no match for 'operator<<' in 'file2 << Frequency(((int)alphabet[p]), num, ((char*)(&a)))' "

I tried to lose the "<<" after the file 2, but it's still giving me an error.
I guess my question is, how to output a void function on a text file?