CODEWITHSUNDEEP
c++vector
Daniel Escobedo
Daniel Escobedo

Reputation: 3

Graph with std::vectors?

I thought that a cool way of using vectors could be to have one vector class template hold an two separate int variables for x/y-coordinates to graph.

example: 

std::vector<int, int> *name*;
// First int. being the x-intercept on a graph
// Second int. being the y-intercept on a graph

(I also understand that I could just make every even/odd location or two separate vectors to classify each x/y-coordinate, but for me I would just like to see if this could work)

However, after making this vector type, I came across an issue with assigning which int within the vector will be written to or extracted from. Could anyone tell me how to best select and std::cout both x/y ints appropriately?

P.S. - My main goal, in using vectors this way, is to make a very basic graph output to Visual Studio terminal. While being able to change individual x/y-intercepts by 'selecting' and changing if needed. These coordinates will be outputted to the terminal via for/while loops.

Also, would anyone like to list out different ways to best make x/y-coordinates with different containers?

Upvotes: 0

Views: 1014

Answers (1)

463035818_is_not_an_ai
463035818_is_not_an_ai

Reputation: 122143

Your question rather broad, in other words it is asking for a bit too much. I will just try to give you some pointers from which you can work your way to what you like.

A) equidistant x

If your x values are equidistant, ie 0, 0.5, 1, 1.5 then there is no need to store them, simply use a

std::vector<int> y;

if the number of variables is not known at compile time, otherwise a 

std::array<int,N> y;

B) arbitrary x

There are several options that depend on what you actually want to do. For simply storing (x,y)-pairs and printing them on the screen, they all work equally well.

map

std::map<int,int> map_x_to_y = { { 1,1}, {2,4}, {3,9}};
// print on screen
for (const auto& xy : map_x_to_y) {
   std::cout << xy.first << ":" xy.second;
}

a vector of pairs

std::vector<std::pair<int,int>> vector_x_and_y = { { 1,1}, {2,4}, {3,9}};

Printing on screen is actually the same as with map. The advantage of the map is that it has its elements ordered, while this is not the case for the vector.

C) not using any container

For leightweight calculations you can consider to not store the (xy) pairs at all, but simply use a function:

int fun(int x) { return x*x; }

TL;DR / more focussed

A vector stores one type. You cannot have a std::vector<int,int>. If you look at the documentation of std::vector you will find that the second template parameter is an allocator (something you probably dont have to care about for some time). If you want to store two values as one element in a vector you either have to use std::vector<std::pair<double,double>> or a different container.

PS

I used std::pair in the examples above. However, I do consider it as good practice to name things whenever I can and leave std::pair for cases when I simply cannot give names better than first and second. In this spirit you can replace std::pair in the above examples with a 

struct data_point {
    int x;
    int y;
};

Upvotes: 1

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