> data(diamonds)
> library(coefplot)
> mod1 <- lm(price ~ carat + cut + x, data=diamonds)
> mod2 <- glm(price > 10000 ~ carat + cut + x, data=diamonds, family=binomial(link="logit"))
> mod3 <- lm(price ~ carat*cut + x, data=diamonds)
> extract.coef(mod1)
Error in UseMethod(generic = "extract.coef", object = model) : 
 no applicable method for 'extract.coef' applied to an object of class "lm"
> extract.coef(mod2)
Error in UseMethod(generic = "extract.coef", object = model) : 
 no applicable method for 'extract.coef' applied to an object of class "c('glm', 'lm')"
> extract.coef(mod3)
Error in UseMethod(generic = "extract.coef", object = model) : 
 no applicable method for 'extract.coef' applied to an object of class "lm"

> sessionInfo()
R version 3.3.3 (2017年03月06日)
Platform: x86_64-w64-mingw32/x64 (64-bit)
Running under: Windows >= 8 x64 (build 9200)
locale:
[1] LC_COLLATE=Polish_Poland.1250 LC_CTYPE=Polish_Poland.1250 LC_MONETARY=Polish_Poland.1250
[4] LC_NUMERIC=C LC_TIME=Polish_Poland.1250 
attached base packages:
[1] grid stats graphics grDevices utils datasets methods base 
other attached packages:
 [1] coefplot_1.2.4 pROC_1.9.1 tidyr_0.6.1 VennDiagram_1.6.17 futile.logger_1.4.3
 [6] Boruta_5.2.0 ranger_0.7.0 tables_0.8 Hmisc_4.0-2 ggplot2_2.2.1 
[11] Formula_1.2-1 survival_2.40-1 lattice_0.20-34 cluster_2.0.6 stringr_1.2.0 
[16] dplyr_0.5.0 magrittr_1.5 readr_1.1.0 
loaded via a namespace (and not attached):
 [1] Rcpp_0.12.10 RColorBrewer_1.1-2 plyr_1.8.4 futile.options_1.0.0 base64enc_0.1-3 
 [6] tools_3.3.3 rpart_4.1-10 digest_0.6.12 tibble_1.3.0 gtable_0.2.0 
[11] htmlTable_1.9 checkmate_1.8.2 Matrix_1.2-8 DBI_0.6-1 useful_1.2.1 
[16] gridExtra_2.2.1 knitr_1.15.1 htmlwidgets_0.8 hms_0.3 nnet_7.3-12 
[21] data.table_1.10.4 R6_2.2.0 foreign_0.8-67 latticeExtra_0.6-28 reshape2_1.4.2 
[26] lambda.r_1.1.9 scales_0.4.1 backports_1.0.5 htmltools_0.3.5 splines_3.3.3 
[31] assertthat_0.2.0 colorspace_1.3-2 labeling_0.3 stringi_1.1.5 acepack_1.4.1 
[36] lazyeval_0.2.0 munsell_0.4.3