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ComputingArray

lookup

viewed 5403 times and licensed 60 times
Array namespace
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Interface

C++

Lookup

 
template<...> BlookupAvalue
std::vector<A>lookup
std::vector<B>result
boolsorted = true )
This function looks up a value in the given vector. When value is found in the lookup vector, the function returns the corresponding value from the result vector. It is equivalent to the vector form of the Microsoft Excel function LOOKUP. If the parameter sorted is set to true, then this function uses a binary search approach to find the value in lookup. If an exact match cannot be found then it returns the next largest value.

Warning

The two vectors lookup and result must be of equal length.

Example:

#include <vector>
#include <iostream>
#include <stdio.h>
#include <codecogs/computing/array/lookup.h>
 
using namespace std;
 
int main()
{
  vector<double> rowA;
  vector<char> rowB;
 
  rowA.push_back(-2.3);
  rowA.push_back(1.37);
  rowA.push_back(1.54);
  rowA.push_back(2.02);
  rowA.push_back(2.17);
 
  rowB.push_back('a');
  rowB.push_back('b');
  rowB.push_back('c');
  rowB.push_back('d');
  rowB.push_back('e');
 
  cout<<"lookup vector:\n";
  for (unsigned int i=0; i<rowA.size(); i++) cout<<rowA[i]<<"\t";
  cout<<"\n";
 
  cout<<"result vector:\n";
  for (unsigned int i=0; i<rowB.size(); i++) cout<<rowB[i]<<"\t";
  cout<<"\n";
 
  cout<<"lookup 1.37=";
  cout<<Array::Search::lookup<double, char>(1.37, rowA, rowB);
  cout<<"\n";
 
  cout<<"lookup 1.36=";
  cout<<Array::Search::lookup<double, char>(1.36, rowA, rowB);
  cout<<"\n";
 
  cout<<"lookup 1.36 (sort=false)=";
  cout<<Array::Search::lookup<double, char>(1.36, rowA, rowB, false);
  cout<<"\n";
 
  cout<<"lookup 2.01=";
  cout<<Array::Search::lookup<double, char>(2.01, rowA, rowB);
  cout<<"\n";
}
Output:
lookup vector:
-2.3    1.37    1.54    2.02    2.17
result vector:
  a       b       c       d       e
  lookup 1.37=b
  lookup 1.36=a
  lookup 1.36 (sort=false)=?
  lookup 2.01=c

Parameters

valuethe value to search for in lookup
lookupa vector of values
resulta vector of values
sortedindicated is the data lookup vector is sorted.

Returns

the result value from the result vector

Authors

Will Bateman (Sep 2005)
Source Code

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