How to get a specified number of local maxima?

function[val,idx]=nthMaxima(P0,n)
%P0 is the array for searching maximus in there 
%n is the number of top maximus to find 
val=zeros(1,n); %defining array for reserving value of maximus
idx=zeros(1,n); %defining array for index of maximus 

for i=1:n
    [val(i),idx(i)]=max(P0);  %taking maximu value and indexing 
    P0(idx(i))=-Inf;          %replacing maxima index with -Inf to search for maxima again
end

%recovering the replaced maxima value 
for j=1:n
    P0(idx(j))=max(j);
end
%done!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
end