lag

问题 Sorry for the long post, but I have provided copy & paste sample data and a possible solution approach below. The relevant part of the question is in the upper part of the post (above the horizontal rule). I have the following table Dt customer_id buy_time money_spent ------------------------------------------------- 2000-01-04 100 11:00:00.00 2 2000-01-05 100 16:00:00.00 1 2000-01-10 100 13:00:00.00 4 2000-01-10 100 14:00:00.00 3 2000-01-04 200 09:00:00.00 10 2000-01-06 200 10:00:00.00 11

问题 I use UIBezierPath for finger painting (my app). I create it using path = [UIBezierPath bezier path]; . It constantly lags on the iPad (and calling it from within drawrect did not change anything). I have been working on this for hours on end and have found no solution, just lag. Would somebody be so kind to help me please? Also, I am using a NSTimer to call the function. That is the old way my app will work so please help me fix this lagggg!!!!! 回答1: Since none of your questions contains

问题 I am trying to create a bunch of lagged variables all at once in data.table. I want these lagged values to be by station and by landcover. I am having some difficulty. Here is my example data.table. require(data.table) r <- structure(list(station = structure(c(1L, 1L, 1L, 1L, 1L, 1L, 2L, 2L, 2L, 2L, 2L, 2L), .Label = c("A", "B"), class = "factor"), landcover = structure(c(2L, 2L, 2L, 4L, 4L, 4L, 1L, 1L, 1L, 3L, 3L, 3L), .Label = c("foam", "Mixed Forest", "other2", "Sand"), class = "factor"),

问题 I've updated Android Studio to version 2.3 yesterday and since after I'm experiencing a slow performance, it was working fine before, though slow when gradle building, but now it taking 100% of processors resources. What is the requirements for Android Studio to run smoothly? My computer runs Windows 7 x64, i7 core, with 8 cores, 10Gb of RAM 回答1: Here you go with three easy steps to get Android Studio Fast : Step 1 : Open gradle.properties file of your app and add in two lines as follows...

问题 I've made the following calculation involving LAG(): (lag(fValue,1,fValue) OVER (PARTITION BY Cluster ORDER BY iSequence) + fValue) / 2 as fValueAjusted It takes the previous (based on iSequence) record's fValue, sums with current one, and divides it by 2. But, instead of using fValue, I must do that using previous record's fValueAjusted. It means that first record's fValueAjusted will be its own fValue. Second record's fValueAjusted will be based on first record's fValue. And, starting from

问题 I'm playing WAVs on my Android phone by loading the file and feeding the bytes into AudioTrack.write() via the FileInputStream > BufferedInputStream > DataInputStream method. The audio plays fine and when it is, I can easily adjust sample rate, volume, etc on the fly with nice performance. However, it's taking about two full seconds for a track to start playing. I know AudioTrack has an inescapable delay, but this is ridiculous. Every time I play a track, I get this: 03-13 14:55:57.100: WARN

问题 I would like to calculate the diff of variables in a data table, grouped by id. Here is some sample data. The data is recorded at a sample rate of 1 Hz. I would like to estimate the first and second derivatives (speed, acceleration) df <- read.table(text='x y id 1 2 1 2 4 1 3 5 1 1 8 2 5 2 2 6 3 2',header=TRUE) dt<-data.table(df) Expected output # dx dy id # NA NA 1 # 1 2 1 # 1 1 1 # NA NA 2 # 4 -6 2 # 1 1 2 Here's what I've tried dx_dt<-dt[, diff:=c(NA,diff(dt[,'x',with=FALSE])),by = id]

问题 0 When I'm building my app, the image loading is very laggy. It seems to happen in conjuction with adding a BottomNavigationView or Toolbar, when they are removed app runs smoothly. Setup is a MainActivity and fragments loaded into it thru bottom nav bar. public class FragmentActivity extends AppCompatActivity { BottomNavigationView navi; FragmentTransaction fragmentTransaction; public static final String TAG = FragmentActivity.class.getSimpleName(); @Override protected void onCreate(Bundle

问题 Below is an example of what I'm trying to achieve in a Redshift Database. I have a variable current_value and I want to create a new column value_desired that is: the same as current_value if the previous row is null equal to the last preceding non-null value if the previous row is non-null It sounds like an easy task but I haven't found a way to do it yet. row_numb current_value value_desired 1 2 3 47 47 4 5 45 45 6 7 8 42 42 9 41 42 10 40 42 11 39 42 12 38 42 13 14 36 36 15 16 17 33 33 18

问题 Does anybody have an explanation for such result using dplyr package? I have a data.frame df library(dplyr) df = data_frame( 'id' = c(1,2,2,2,2,3,3,3,3), 'start' = c(881, 1611, 1611, 1642, 1764, 0, 0, 28, 59), 'end' = c(1089, 1819, 1819, 1850, 1972, 208, 208,236, 267)) That looks like # Source: local data frame [9 x 3] # # id start end # (dbl) (dbl) (dbl) # 1 1 881 1089 # 2 2 1611 1819 # 3 2 1611 1819 # 4 2 1642 1850 # 5 2 1764 1972 # 6 3 0 208 # 7 3 0 208 # 8 3 28 236 # 9 3 59 267 After