CODEWITHSUNDEEP
r
user1062293
user1062293

Reputation: 133

How to export breakpoints index into a vector from strucchange package?

I'm using the strucchange package in order to determine where my curve model segments.

My code looks like this:

l.fit <- loess(data$y~data$x)
px <- predict(l.fit,newdata=data$x)
bp <- breakpoints(px~1)

Now, the output of bp:

Optimal 6-segment partition: 

Call:
breakpoints.formula(formula = px ~ 1)

Breakpoints at observation number:
161 254 347 440 533 

Corresponding to breakdates:
0.2571885 0.4057508 0.5543131 0.7028754 0.8514377

The breakdates are kind of useless, as my x scale goes from 1 to 700 or so. But the breakpoints themselves are exactly what I want, specifically the last one, 533.

If i type:

bp[1]

I get:

$breakpoints
[1] 161 254 347 440 533

but if I try to assign bp[1] to a new vector, I get nothing. Is there anyway I can isolate the last breakpoint, i.e. 533, and assign it to a variable so I can plot a vertical line at the breakpoint? I need to do this for a couple hundred datasets, so being able to isolate the breakpoints would be really useful.

Thanks!

Upvotes: 1

Views: 619

Answers (2)

IRTFM
IRTFM

Reputation: 263481

I cannot tell whether you are so new at R that you think that the fact that executing this code should produce any console output:

vec <- bp[1]

What happens if you now type:

vec

You should be using either bp[["breakpoints"]][5] or bp$breakpoints[5] to get the last breakpoint. You would then want to use it as an index into data$x :

 data$x[ bp$breakpoints[5] ]

If you are doing this "programmatically" it might be safer to use the [["quoted-name"]] version of access, since the $ version has some under-appreciated gotcha's.

Upvotes: 0

James
James

Reputation: 66874

[ extraction doesn't drop to the simpliest form, so it remains a list. Use [[ or $ extraction instead to get a numeric vector.

bps <- bp[[1]]

or

bps <- bp$breakpoints

To get the last one, you would need to either count its length and select the last one, or reverse it and select the first:

bps[length(bps)]

or

rev(bps)[1]

Upvotes: 4

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