I have a scenario where the user can pick up to 5 different data sets to be included at one time. These data sets have vastly different scales (one might be from 0-100 while another could be 500-6000, and so on). These data sets are sensor readings (temperature, PH, etc.).
They all share a common x-axis in that each data set has different points across time, which is the x-axis. In addition to this, I want to correlate all of these different data sets with another data set that is basically a set of activities that happened at certain points in time, so I want to be able to say "for each event, what were the different sensor readings at that time" in a nice, graphical way.
What would be the best type of graph in highcharts to be able to display these? Obviously, a regular line graph doesn't work because of the different scales. A dual axis chart isn't enough. I've been playing around with a bunch of different stuff, but I haven't found anything that looks good.
In my app, i got core plot bar chart on a scroll view with paging, on IPhone all work fine , you page between different pages, one of them is the plot with its own touch gestures and properties.
Problem starts when i run the same code on IPad. plot becomes slow and laggy, all touch gestures takes a lot of time to response and the whole scroller paging becomes heavy and slow.
the chart itself contains 100 points or so (not so big).
I've read somewhere that the change of plot space between IPhone and IPad makes these changes in performance because the IPad renders 4 times the graphics. Did anybody had this problem before? Is there something i can do to make performance better on IPad without limit or lose preform data?
Unfortunately Core plot is a very slow library which can only handle a few hundred data-points (or less in some cases).
I wrote an answer here which describes a performance comparison between iOS chart components. One of the charts tested was core-plot and it couldn't do the first test!
Without knowing the specifics of your app, here are some general performance hints:
Set all line styles and fills that you don't need to nil rather than transparent colors.
Use solid color fills rather than gradients or images where possible.
Reduce the number of axis labels, tick marks, and grid lines if possible. Perhaps eliminate minor tick marks and grid lines completely (set the corresponding line styles to nil).
Only call -reloadData when a significant portion of the plot data changes. Use the insert and delete methods when possible. See the "Real Time Plot" in the Plot Gallery example app.
For the last week I've been attempting to write some code in which I'd be able to trace an image and compare it with the original by pixel color count. So far the only two definite thing working is the drawing and pixel count (which obviously returns 0 since the rest isn't working)
To make the UIImageView of the drawing into a PNG for comparison I take a screenshot.However, I'm trying to call the saved drawing (screenshot) immediately after the save for a pixel color count and comparison. This whole process is not working whatsoever.
The pixel count code asks for a PNG at the moment,so I'm trying to work around that.
Is there maybe an easier way to do this whole process instead of first taking a screenshot, then calling it and then getting the pixel color count? I'm trying to make the code as simple as possible by comparing only two colors.
Any help would be appreciated. I would post code, but I'd rather get a fresh take on this since I've tried many different ways already. Thanks in Advance.
At first I think my question should have been asked before, but I didn't find what I want.
One element of this iOS app I'm developing is break a 8x8 grid into Tetris pieces (every piece is made of 4 blocks). Two particular question I have are:
what is the best way to represent a Tetris piece in objective-C?
what algorithm to present the grid into random Tetris pieces (and later on how to check if two pieces fits together).
Edition on 01/28
#livingtech, I think I implemented pretty much what you say, except the point of "having a hole". My code works with no hole at simple stage when Tetris block is two blocks only (yes, two squares, connected either horizontally or vertically), but at 3-square Tetris block, I would get holes. I just tested and out of 1000 running, I would get one without a hole. So definitely I need some mechanism to check if next square will be a singleton.
I been trying to do the same thing for my game. Though I am a total beginner, and I'm using XNA and C#.
But the way I'm trying to go about it is: 4x6 grid array
--y123456
X1-000000
X2-000000
X3-000000
X4-000000
Here,
0 signifies no block
1 defines a block
Algorithm
Start by taking the very first 0 in the array ( top left corner )
and randomly pick a 0 or a 1.
Randomly choose the coordinates based on x1/x2-y1/y2, decide 1 or 0.
If it is 1, then decide coordinated based on where that 1 was put.
If it was 1 on x2 y1, then decide if a 1 should go on next touching
coordinate.
If you just have to code in what coordinates touch and which don't,
and the logic will roll through.
I have mine set up bit different. But this is the basic foundation of my random Tetris engine.
I also found that making it like that really helps to have a whiteboard and make a drawing of the grid and label with your coordinates.
since ur board is 8*8, i think u can use a int64 to represent the board. each bit of the int64 represents whether the specific grid is filled or not.
Implementing Tetris is a hobby of mine. First implemented it in Windows/C. Then in Perl/Tk! Last implementation I did in Obj-C/Cocoa (Mac). In all cases, the game logic is the same. Only the UI stuff changes. I treat every little box separately and have a two-dimensional array which contains the presence (and color) of every "set" box on the board. Standard board size I use is 10 boxes wide by 20 boxes high.
Separately I keep track of the "dropping" piece: it's location and what kind of piece it is. Based on a timer, try to make the piece drop. If any of the boxes where the "dropping" piece would drop is already set, then stop dropping the piece and add the piece boxes to the "set" part of the board. Create a new piece, and start over.
It may not be the best way to implement it, but it makes sense in my head. From a pure OO perspective, each shape of a dropping piece could be a subclass of a generic shape class. Override functions that check whether the shape can drop, the offsets of the individual boxes in the shape, etc.
I don't think anybody has taken a stab at your question #2 yet here, so I'm going to outline what I would do.
Setup:
You'll need to represent your grid as an array of some kind. At the very least, you'll want some kind of boolean values, to denote whether each coordinate in the grid is "occupied".
You'll need to keep track of the pieces on your grid. This could be another array, this time holding references to the four coordinates for each piece.
You'll need a variable or variables to keep track of a coordinate in your grid where you'll start filling in pieces, (I would probably populate these with a corner to start).
Set up a "pool" of all possible Tetris pieces and rotations. (You'll want to keep track of which ones you've already checked on every iteration outlined below.)
Iterate:
Get a random piece from your pool that will fit into your starting coordinate. (If you want to get fancy, you could be smart about which ones you choose, or you could just go totally random. As pieces don't fit, mark them checked, so you don't keep checking randomly forever. If you get to a point where you've checked all the pieces, you have a solution that doesn't work, either back up an iteration, or start over.)
Make sure the Tetris piece you selected didn't leave a "hole", or empty space with less than 4 squares. (I don't know your requirements for solving this problem, so I can't say whether you should focus on speed or ease of coding, but you may be able to skip this step if you want, and "brute force" the solution.)
"Place" the piece, by writing it to your piece array and marking the coordinates filled.
Check for "finished" condition, in which all your spaces are filled.
Pick a new coordinate in your grid and repeat #1. (I would pick an empty one next to the previous coordinate.)
If this actual yet, I wrote test tetris app on Objective-C few months ago https://github.com/SonnyBlack/Test-Demo-Tetris . I think my algorithm not very well, but it working. =)
I have a simple scatter plot with ~500,000 points on it. Having this many points on the graph really makes my app lag, which isn't surprising. I was wondering if there was a way to only draw the points for a specific x range (like 0-100 or 500-1000). The user will only be looking at certain points of the graph (via zooming in), so it would make it much less laggy if the program only had to plot a small amount of those points.
I've tried having the graph re-draw itself, every time the user zooms in/out or moves the axis, but this actually seems to make the app run slower. Is there a solution to this issue?
You'll have to filter the data and only provide the visible points to the plot in your datasource. Use a plot space delegate to detect when the visible area changes and adjust the data as needed. The best way to do this will depend on how your app stores its data internally. You'll want to use a data structure that lets you quickly determine which points need to be plotted.
You don't want to reload all of the data every time something changes. The plots have methods to insert and remove ranges of data points while preserving the rest of the data. If you're only changing a few points at a time, this is much faster than reloading all of the data every time. The "Real-Time Plot" demo in the Plot Gallery app shows one way to use these methods.