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    sapply function in R help

    I have read two .csv files and did some editing. >a1<-read.csv("2013.csv",header=T, na.strings = c("NULL","PrivacySuppressed")) >a2<-a1[,441,drop=F] >a3<-a1[,-441,drop=F] >a4<-cbind(a1,a2) >a4<-a4[, colSums(is.na(a4)) != nrow(a4)] > mode(a4) >[1] "list" I need the a4 to be...
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    Covariance of Time Series

    Could someone explain if this is the right way to do it? Thank you! https://goo.gl/photos/ykmodDUj7RVKcS4W9
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    Time Series (Random Walk?)

    I just recently started to learn about moving average process of order 1, however, I get confused if there are other things attached to the equation. 1. For example: Z_t = 8 + 2t + 5X_t where X_t is a zero-mean stationary series with autocovariance function r_k a) Find the mean function and...
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    Time Series (White Noise)

    Suppose W_t and Y_t are two independent normal white noise series with Var(W_t)=2Var(Y_t)=4. Let X_t = W_t-0.5W_{t-1} and Z_t=Y_t+0.4Y_{t-1}-0.4Y_{t-2}. Put V_t=X_t-Z_t. Find the Cov(V_t,V_{t-1}), k=0,1,2,3,.. So I tried doing this...