[R] Extracting slots from an object (e.g.: object produced by unit root test function "urdfTest")

[jpm miao]

Hi,

   I run a statistical test function in the package "fUnitRoots" that
returns a S4 object but I am wondering how to extract the p-value, one of
the output elements.

The document of the function "urdfTest":
.....
All tests return an object of class "fHTEST" with the following slots:

@call
.....
@test
a list object which holds the output of the underlying test function.
@title
.....
The entries of the @test slot include the following components:

$statistic
......
$p.value
the p-value of the test.
.....
(end)

   I store the result of the test test in an element of a list
(adf1["r3m"][[1]]), and I want to extract the p-value. I was expecting the
p-value via adf1["r3m"][[1]]@test$p.value but it gives only an error
message. Could someone tell me how to extract the p-value? Thanks!!!

>adf1["r3m"][[1]]<-urdfTest(dat[,i], lags = 1, type = "ct")
> adf1["r3m"][[1]]
 [1] "  "
 [2] "  Test regression trend "
 [3] "  "
 [4] "  Call:"
 [5] "  lm(formula = z.diff ~ z.lag.1 + 1 + tt + z.diff.lag)"
 [6] "  "
 [7] "  Residuals:"
 [8] "      Min      1Q  Median      3Q     Max "
 [9] "  -3.0785 -0.0485  0.0072  0.0627  3.5672 "
[10] "  "
[11] "  Coefficients:"
[12] "                Estimate Std. Error t value Pr(>|t|)    "
[13] "  (Intercept) -1.733e-02  9.529e-03  -1.818  0.06910 .  "
[14] "  z.lag.1     -7.060e-03  2.343e-03  -3.013  0.00261 ** "
[15] "  tt           5.299e-06  4.927e-06   1.076  0.28221    "
[16] "  z.diff.lag  -1.035e-01  1.859e-02  -5.569 2.81e-08 ***"
[17] "  ---"
[18] "  Signif. codes:  0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1"
[19] "  "
[20] "  Residual standard error: 0.2107 on 2864 degrees of freedom"
[21] "  Multiple R-squared:  0.01461,\tAdjusted R-squared:  0.01358 "
[22] "  F-statistic: 14.15 on 3 and 2864 DF,  p-value: 3.716e-09"
[23] "  "
[24] "  "
[25] "  Value of test-statistic is: -3.0134 3.0697 4.5828 "
[26] "  "
[27] "  Critical values for test statistics: "
[28] "        1pct  5pct 10pct"
[29] "  tau3 -3.96 -3.41 -3.12"
[30] "  phi2  6.09  4.68  4.03"
[31] "  phi3  8.27  6.25  5.34"

> adf1["r3m"][[1]]@test
Error: trying to get slot "test" from an object of a basic class
("character") with no slots
> adf1["r3m"][[1]]@test$p-value
Error: trying to get slot "test" from an object of a basic class
("character") with no slots

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