Use new data_grid instead of expand

model-basics.Rmd

@@ -45,7 +45,7 @@ The goal of a model is not to uncover truth, but to discover a simple approximat
 
 We need a couple of packages specifically designed for modelling, and all the packages you've used before for EDA. 
 
-```{r setup, message = FALSE}
+```{r setup, message = FALSE, cache = FALSE}
 # Modelling functions
 library(modelr)
 options(na.action = na.warn)
@@ -53,7 +53,6 @@ options(na.action = na.warn)
 # EDA tools
 library(ggplot2)
 library(dplyr)
-library(tidyr)
 ```
 
 ## A simple model
@@ -243,10 +242,10 @@ It's also useful to see what the model doesn't capture, the so called residuals
 
 ### Predictions
 
-To visualise the predictions from a model, we start by generating an evenly spaced grid of values that covers the region where our data lies. The easiest way to do that is to use `tidyr::expand()`. Its first argument is a data frame, and for each subsequent argument it finds the unique variables and then generates all combinations:
+To visualise the predictions from a model, we start by generating an evenly spaced grid of values that covers the region where our data lies. The easiest way to do that is to use `modelr::data_grid()`. Its first argument is a data frame, and for each subsequent argument it finds the unique variables and then generates all combinations:
 
 ```{r}
-grid <- sim1 %>% expand(x) 
+grid <- sim1 %>% data_grid(x) 
 grid
 ```
 
@@ -377,7 +376,7 @@ We can fit a model to it, and generate predictions:
 mod2 <- lm(y ~ x, data = sim2)
 
 grid <- sim2 %>% 
-  expand(x) %>% 
+  data_grid(x) %>% 
   add_predictions(mod2)
 grid
 ```
@@ -416,7 +415,7 @@ When you add variables with `+`, the model will estimate each effect independent
 
 To visualise these models we need two new tricks:
 
-1.  We have two predictors, so we need to give `expand()` two variables. 
+1.  We have two predictors, so we need to give `data_grid()` both variables. 
     It finds all the unique values of `x1` and `x2` and then generates all
     combinations. 
    
@@ -429,7 +428,7 @@ Together this gives us:
 
 ```{r}
 grid <- sim3 %>% 
-  expand(x1, x2) %>% 
+  data_grid(x1, x2) %>% 
   gather_predictions(mod1, mod2)
 grid
 ```
@@ -467,7 +466,7 @@ mod1 <- lm(y ~ x1 + x2, data = sim4)
 mod2 <- lm(y ~ x1 * x2, data = sim4)
 
 grid <- sim4 %>% 
-  expand(
+  data_grid(
     x1 = seq_range(x1, 5), 
     x2 = seq_range(x2, 5) 
   ) %>% 
@@ -475,7 +474,7 @@ grid <- sim4 %>%
 grid
 ```
 
-Note my use of `seq_range()` inside `expand()`. Instead of using every unique value of `x`, I'm going to use a regularly spaced grid of five values between the minimum and maximum numbers. It's probably not super important here, but it's a useful technique in general. There are two other useful arguments to `seq_range()`:
+Note my use of `seq_range()` inside `data_grid()`. Instead of using every unique value of `x`, I'm going to use a regularly spaced grid of five values between the minimum and maximum numbers. It's probably not super important here, but it's a useful technique in general. There are two other useful arguments to `seq_range()`:
 
 *  `pretty = TRUE` will generate a "pretty" sequence, i.e. something that looks
     nice to the human eye. This is useful if you want to produce tables of 
@@ -554,7 +553,7 @@ model_matrix(df, y ~ poly(x, 2))
 
 However there's one major problem with using `poly()`: outside the range of the data, polynomials rapidly shoot off to positive or negative infinity. One safer alternative is to use the natural spline, `splines::ns()`.
 
-```{r}
+```{r, cache = FALSE}
 library(splines)
 model_matrix(df, y ~ ns(x, 2))
 ```
@@ -581,7 +580,7 @@ mod4 <- lm(y ~ ns(x, 4), data = sim5)
 mod5 <- lm(y ~ ns(x, 5), data = sim5)
 
 grid <- sim5 %>% 
-  expand(x = seq_range(x, n = 50, expand = 0.1)) %>% 
+  data_grid(x = seq_range(x, n = 50, expand = 0.1)) %>% 
   gather_predictions(mod1, mod2, mod3, mod4, mod5, .pred = "y")
 
 ggplot(sim5, aes(x, y)) + 
@@ -610,7 +609,7 @@ sim6 <- tibble(
 mod <- lm(y ~ x1 * x2, data = sim6)
 
 grid <- sim6 %>% 
-  expand(
+  data_grid(
     x1 = seq_range(x1, 10),
     x2 = c(0, 0.5, 1, 1.5)
   ) %>% 

model-building.Rmd

@@ -86,7 +86,7 @@ Then we look at what the model tells us about the data. Note that I back transfo
 
 ```{r}
 grid <- diamonds2 %>% 
-  expand(carat = seq_range(carat, 20)) %>% 
+  data_grid(carat = seq_range(carat, 20)) %>% 
   mutate(lcarat = log2(carat)) %>% 
   add_predictions(mod_diamond, "lprice") %>% 
   mutate(price = 2 ^ lprice)
@@ -213,7 +213,7 @@ One way to remove this strong pattern is to use a model. First, we fit the model
 mod <- lm(n ~ wday, data = daily)
 
 grid <- daily %>% 
-  expand(wday) %>% 
+  data_grid(wday) %>% 
   add_predictions(mod, "n")
 
 ggplot(daily, aes(wday, n)) + 
@@ -340,7 +340,7 @@ We can see the problem by overlaying the predictions from the model on to the ra
 
 ```{r}
 grid <- daily %>% 
-  expand(wday, term) %>% 
+  data_grid(wday, term) %>% 
   add_predictions(mod2, "n")
 
 ggplot(daily, aes(wday, n)) +
@@ -372,7 +372,7 @@ library(splines)
 mod <- MASS::rlm(n ~ wday * ns(date, 5), data = daily)
 
 daily %>% 
-  tidyr::expand(wday, date = seq_range(date, n = 13)) %>% 
+  data_grid(wday, date = seq_range(date, n = 13)) %>% 
   add_predictions(mod) %>% 
   ggplot(aes(date, pred, colour = wday)) + 
     geom_line() +