curve_intersect: "Error in approxfun", when one of the curves is a vertical line

[csapot]

I'm trying the following code:

> curve1_temp
      x   y
165 885 621
166 886 622
167 887 622
168 888 623
169 889 623
170 890 624
171 891 624
172 892 626
173 893 627
174 894 627
175 895 628

> line1_temp
    x   y
1 889 610
2 889 630

and the result of curve_intersect is:

> intersect1_temp = curve_intersect(curve1_temp, line1_temp)
Error in approxfun(curve2$x, curve2$y, rule = 2) : 
  need at least two non-NA values to interpolate

based on visual plotting, the two curves should have an intersect:

ggplot(data = curve1_temp, aes(x = x, y = y)) + geom_line(color = "red") + geom_line(data = line1_temp, aes(x = x, y = y), color = "green")

Can you please help what can be the issue?

[csapot]

seems that the 'approxfun' function can't interpolate values where the x-coordinates are the same.
https://stackoverflow.com/questions/44386686/interpolation-function-approx-in-r-gives-error-need-at-least-two-non-na-valu