+/* An NP or DNP plot. */
+struct np_plot_chart
+ {
+ struct chart_item chart_item;
+ struct casereader *data;
+ bool detrended;
+
+ /* Copied directly from struct np. */
+ double y_min, y_max;
+ double dns_min, dns_max;
+
+ /* Calculated. */
+ double slope, intercept;
+ double y_first, y_last;
+ double x_lower, x_upper;
+ double slack;
+ };
+
+struct chart_item *np_plot_create (const struct np *,
+ const struct casereader *,
+ const char *label);
+struct chart_item *dnp_plot_create (const struct np *,
+ const struct casereader *,
+ const char *label);
+\f
+/* This boilerplate for np_plot_chart, a subclass of chart_item, was
+ autogenerated by mk-class-boilerplate. */
+
+#include <assert.h>
+#include "libpspp/cast.h"
+
+extern const struct chart_item_class np_plot_chart_class;
+
+/* Returns true if SUPER is a np_plot_chart, otherwise false. */
+static inline bool
+is_np_plot_chart (const struct chart_item *super)
+{
+ return super->class == &np_plot_chart_class;
+}
+
+/* Returns SUPER converted to np_plot_chart. SUPER must be a np_plot_chart, as
+ reported by is_np_plot_chart. */
+static inline struct np_plot_chart *
+to_np_plot_chart (const struct chart_item *super)
+{
+ assert (is_np_plot_chart (super));
+ return UP_CAST (super, struct np_plot_chart, chart_item);
+}
+
+/* Returns INSTANCE converted to chart_item. */
+static inline struct chart_item *
+np_plot_chart_super (const struct np_plot_chart *instance)
+{
+ return CONST_CAST (struct chart_item *, &instance->chart_item);
+}
+
+/* Increments INSTANCE's reference count and returns INSTANCE. */
+static inline struct np_plot_chart *
+np_plot_chart_ref (const struct np_plot_chart *instance)
+{
+ return to_np_plot_chart (chart_item_ref (&instance->chart_item));
+}
+
+/* Decrements INSTANCE's reference count, then destroys INSTANCE if
+ the reference count is now zero. */
+static inline void
+np_plot_chart_unref (struct np_plot_chart *instance)
+{
+ chart_item_unref (&instance->chart_item);
+}
+
+/* Returns true if INSTANCE's reference count is greater than 1,
+ false otherwise. */
+static inline bool
+np_plot_chart_is_shared (const struct np_plot_chart *instance)
+{
+ return chart_item_is_shared (&instance->chart_item);
+}