Getting distorted curves when attempting to plot multiple curves in the same plot

[eperkan]

Thanks @albertopessia for this user-friendly and well-documented package.

When I try to plot multiple dose-response curves in the same plot, the curves get distorted - due to change(s) in x or y axes. Consider the following example:

# Data
dose <- c( -4, -4.30, -4.60, -4.90, -5.20, -5.50, -5.80, -6.10, -6.40, -6.70, -7)
response <- c(3, 10, 24, 32, 45, 58, 71, 88, 92, 95, 99)

# Model 1
m1 <- drda(formula = response ~ dose, mean_function = "logistic4")

# Model 2
low_bound <- c(0, 100, -7, -Inf)
up_bound <- c(0, 100, -4, Inf)
m2 <- drda(formula = response ~ log_dose, upper_bound = up_bound, lower_bound = low_bound)

# Plot
plot(m1, m2) 

Defining axis limits appears to be the only working solution:

plot(m, m2, 
        xlim = c(-7, .4), 
        ylim = c(0, 100), 
        legend = c("Model_1", "Model_2")) 

Is there something obvious I am missing here or is this the expected behavior?

> sessionInfo()
R version 4.0.2 (2020-06-22)
Platform: x86_64-apple-darwin17.0 (64-bit)
Running under: macOS  10.16

Matrix products: default
LAPACK: /Library/Frameworks/R.framework/Versions/4.0/Resources/lib/libRlapack.dylib

locale:
[1] en_US.UTF-8/en_US.UTF-8/en_US.UTF-8/C/en_US.UTF-8/en_US.UTF-8

attached base packages:
[1] stats     graphics  grDevices utils     datasets  methods   base     

other attached packages:
[1] pracma_2.3.3 drda_1.0.0  

loaded via a namespace (and not attached):
 [1] fansi_0.5.0      assertthat_0.2.1 dplyr_1.0.7      crayon_1.4.1     utf8_1.2.2      
 [6] grid_4.0.2       R6_2.5.1         DBI_1.1.1        lifecycle_1.0.1  gtable_0.3.0    
[11] magrittr_2.0.1   scales_1.1.1     pillar_1.6.4     ggplot2_3.3.5    rlang_0.4.11    
[16] generics_0.1.0   vctrs_0.3.8      ellipsis_0.3.2   tools_4.0.2      glue_1.4.2      
[21] purrr_0.3.4      munsell_0.5.0    tinytex_0.34     xfun_0.26        compiler_4.0.2  
[26] pkgconfig_2.0.3  colorspace_2.0-2 tidyselect_1.1.1 tibble_3.1.5  

[albertopessia]

Hi @eperkan, thank you for your message.

When you call plot(m1, m2) the function is trying its best to automatically choose a good range for both axis. Sometimes, like in your case, it fails to find a good-looking option. The solution is to choose manually the preferred range, like you correctly guessed.

I have instead the following comments to your example:

• m2 does not look a very good fit because of the growth rate range you chose. Try to fix only the minimum and maximum of the curve and leave the growth rate free to vary.
• you can move the legend to a more convenient location using the argument legend_location, for example plot(m1, m2, xlim = c(-7, 1), legend = c("Model 1", "Model 2"), legend_location = "topright")

I hope my reply answers your questions.

Happy new year!

[albertopessia]

Closing the issue as no further comments were given.