@msheaver - The line
let context = UIGraphicsGetCurrentContext()
only gives you a handle to the current context being used by draw(_:). draw(_:) always draws into its context, so the context is always there.
@caroline, I thought that that was the case, and many thanks for confirming it for me!
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Thanks for the great tutorial.I have to set the Y axis minimum and maximum value .How can i do that?
I donât think I understand the question. The y axis maxValue is taken from the maximum value in graphPoints, but you could change that, and you could set a minimum value and change the position calculations accordingly.
yes ,i need to set custom y axis min valueâŠCurrently its 0âŠI have no idea to change that minimum value.
@anishparajuli - I still donât understand. Even with a minimum value, the graph would look the same, just the label containing 0 on the right hand side would have a different value.
The y points are calculated here:
let columnYPoint = { (graphPoint:Int) -> CGFloat in
var y:CGFloat = CGFloat(graphPoint) /
CGFloat(maxValue) * graphHeight
y = graphHeight + topBorder - y // Flip the graph
return y
I guess you could add a minimum value to the returned y point if thatâs what youâre after.
@caroline
Ok i will be more simplerâŠ
//Weekly sample data
var graphPoints:[Int] = [4, 2, 6, 4, 5, 8, 3]
As in the tuorial the y axis range is from 0 to 8âŠ
How can i set graph y-axis values between 2 to 6?
@anishparajuli - Iâm not very good at maths, but something like this seems to work:
let maxValue = 6
let minValue = 2
let columnYPoint = { (graphPoint:Int) -> CGFloat in
var y:CGFloat = CGFloat(graphPoint - minValue) /
CGFloat(maxValue - minValue) * graphHeight
y = graphHeight + topBorder - y // Flip the graph
return y
}
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@caroline WowâŠThanks a lot.It works.
I appreciate your time.Have a nice day
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When you drag the UITapGestureRecognizer to the Container view, why does it show up at the very bottom of the object hierarchy, instead of being âinsideâ the Container view object? (well, that answer is obvious - âit just doesâŠâ) That would seem that having the gesture recognizer create/indicate a recognizer that only functioned within a particular view.
(If Cocoa Touch can do this that is. Of course, Apple already did 20 years ago on the Newton with TRecognizer::EnableArea(RecArea*, RefArg)⊠(Iâm guessing, since TRecognizer is sadly isnât documented, as with the rest of the NewtonOS) Maybe theyâve forgotten? 
@jimw338 - It just does 
It annoys me too. But I guess objects that arenât views donât go into the hierarchy.
Firstly, thank you for this wonderful tutorial. This is the best and in-depth tutorial I could find online about plotting.
My question is regarding the block of code below:
//Draw the circles on top of graph stroke
for i in 0..<graphPoints.count {
var point = CGPoint(x:columnXPoint(i), y:columnYPoint(graphPoints[i]))
point.x -= 5.0/2
point.y -= 5.0/2
let circle = UIBezierPath(ovalInRect:
CGRect(origin: point,
size: CGSize(width: 5.0, height: 5.0)))
circle.fill()
}
How can I modify this code to add different labels to each data point like the one below:
Could you please help me in this regard.
I have posted this in StackOverFlow with many related questions. It would be great if you can help with them as well.
Iâve up to the point that sets the UILabels text, after figuring out what changes Apple has made to the calendar classes. I want to programmatically space the labels out. I can set the view.center coordinates easily enough, so thatâs one way.
I read somewhere (canât find it right now) that thereâs not a way to âevenly space viewsâ with auto-constraints, without using transparent âspacerâ views between then. The view in question was a keyboard and the question was about spacing the keys.
Can I use auto-constraint to make (in IB or in code) a single constraint that would apply to multiple views? In this case, it would be a vertical-center-to-GraphView-edge constraint on all the labels at once.
Also, is there a method called when the view is resized? (Although the iOS doesnât [yet?] have a multiple-window interface except for side-by-side mode). Is this âlayoutMarginsDidChangeâ? Or is âdrawâ just called again?
@jimw338 - you donât have to use âspacerâ views any more - iOS 9 introduced layout guides.
I wrote a tutorial on coding constraints, but it doesnât mention layout guides very much:
https://www.raywenderlich.com/125718/coding-auto-layout
You might be looking for layoutSubviews(). This is called after constraints have been calculated, and calculates frames for views. (This is mentioned in the above tutorial.)
@ecoapps - thank you for the kind words.
You have the x and y points where the circles are drawn. So all you have to do is either draw the text as in my example below, or if you want labels or buttons, put them in an array and work out the corresponding points and change the center property of the labels.
I added a property to the view:
var labelText: [NSString] = ["A", "B", "C", "D", "E", "F", "G"]
Then in the for loop that you quoted above, I added this at the end:
let textPoint = CGPoint(x: point.x, y: point.y + 8)
labelText[i].draw(at: textPoint, withAttributes: nil)
This resulted in this graph:
This obviously needs a bit of cleaning up as to exact text positions and colors, but thatâs the general principle.
Edit: SwiftCharts looks pretty good.
@caroline
Thank you for your reply and sharing the code to add labels at data points. I tried adding your code in the locations below. However, as you can see, I am getting an error message. Not sure how to resolve it. Could you please help.
Ah - I was using Xcode 8 and Swift 3. If youâre on Swift 2, then itâs drawAtPoint. This one:
https://developer.apple.com/reference/foundation/nsstring/1533109-drawatpoint
labelText[i].drawAtPoint(textPoint, withAttributes: nil)
(I think)
Hi Caroline!
Thank you for the great tutorial!
Do you know if i can use the graph in this style for one of my apps or will apple reject it when i submit it to the app store because it looks like their graphs in the health app?
@max_w - I havenât submitted myself, but from memory there are a number of apps that use the same style of graph (I canât find one now!). I donât think it would be grounds for rejection if the app is not a complete clone.
However - the style of apps has slightly changed now to use fewer gradients. For example the graph in this app from Runtastic: