Nikkei 225 and its theoretical model.

I have lost my interest to Nikkei 225 some time ago. But revisit today and found that it is  overpriced more than 10%. Dangerous. #nikkei225

# prapare datas.

getSymbols("NIKKEI225",src="FRED")
N225 <- NIKKEI225
getSymbols("^GSPC")
getSymbols("YJUSDJPY",src="yahooj")

# or

getFX("USD/JPY")
YJUSDJPY <- USDJPY


> k3
[1] "2007-01-01::2017-09-30"
> summary(lm(to.monthly(N225[k3])[,4] ~  to.monthly(GSPC[k3])[,4] + to.monthly(YJUSDJPY[k3])[,4]))

Call:
lm(formula = to.monthly(N225[k3])[, 4] ~ to.monthly(GSPC[k3])[,
    4] + to.monthly(YJUSDJPY[k3])[, 4])

Residuals:
     Min       1Q   Median       3Q      Max
-2076.79  -388.69    57.57   500.26  1723.19

Coefficients:
                                Estimate Std. Error t value Pr(>|t|) 
(Intercept)                   -9754.2106   457.2093  -21.33   <2e-16 ***
to.monthly(GSPC[k3])[, 4]         4.4559     0.1835   24.28   <2e-16 ***
to.monthly(YJUSDJPY[k3])[, 4]   163.5134     5.7013   28.68   <2e-16 ***
---
Signif. codes:  0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1

Residual standard error: 723.8 on 126 degrees of freedom
Multiple R-squared:  0.9672, Adjusted R-squared:  0.9667
F-statistic:  1858 on 2 and 126 DF,  p-value: < 2.2e-16