Fit Annotations on MKMapView part - ios

Question

I got MKMapView and a number of annotations on it. I use next code for displaying all annotations:
NSArray *coordinates = [self.mapView valueForKeyPath:#"annotations.coordinate"];
CLLocationCoordinate2D maxCoord = {-90.0f, -180.0f};
CLLocationCoordinate2D minCoord = {90.0f, 180.0f};
for(NSValue *value in coordinates) {
CLLocationCoordinate2D coord = {0.0f, 0.0f};
[value getValue:&coord];
if(coord.longitude > maxCoord.longitude) {
maxCoord.longitude = coord.longitude;
}
if(coord.latitude > maxCoord.latitude) {
maxCoord.latitude = coord.latitude;
}
if(coord.longitude < minCoord.longitude) {
minCoord.longitude = coord.longitude;
}
if(coord.latitude < minCoord.latitude) {
minCoord.latitude = coord.latitude;
}
}
MKCoordinateRegion region = {{0.0f, 0.0f}, {0.0f, 0.0f}};
region.center.longitude = (minCoord.longitude + maxCoord.longitude) / 2.0;
region.center.latitude = (minCoord.latitude + maxCoord.latitude) / 2.0;
region.span.longitudeDelta = (maxCoord.longitude - minCoord.longitude) * 1.5;
region.span.latitudeDelta = (maxCoord.latitude - minCoord.latitude) * 1.5;
[self.mapView setRegion:region animated:YES];
This code centers all annotations - perfect. But what if I want to fit annotations, lets say, on right half part of map. Is there any way to do that?
Here how it's now:
Here what I want to achieve:

Answer 1

If your target area is always to the left or right (i.e. still allowing full height) then it is very easy, you just need to work out the maths for your region's boundaries.
Let's assume you want the pins to be in the right-hand quarter of the page. This would mean you need to tell the map to view a region 4x (targetspan/currentspan) bigger than the pin region and with the middle of that region being shifted left by 1.5x ((targetspan-currentspan)/2)the width of the region. (I'm going to sat latitude is from 0 to 1 but really you just use what ever you have calculated already)
Imagine the view being divided into four vertical strips, there would be 5 lines. The left edge of the screen is 0, the next line is 1, the middle is 2, the next is 3 and the last is 4.
You want your pins to be between lines 3 and 4, meaning the longitude span you calculated above is 1 unit wide and the center.longitude is at 3.5.
You have a region that is ((3.5,0.5), (1,1)) and you need to tell your map to zoom to the region ((2,0.5),(4,1)). So, get the longitudeDelta, multiply it by 1.5 and subtract that from the center.longitude, that is your new target center.longitude. Then multiply the longitudeDelta by 4 and that is your new longitudeDelta.
You can do something similar with latitude on a small scale, but on a large scale the calculations ned to take into account the map projection which means the pixels near the equator represent more land than those near the poles.