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docs/src/tutorials/getting_started/getting_started_with_JuMP.jl

@@ -319,6 +319,14 @@ end                         #hide
 
 @variable(model, a[1:2, 1:2])
 
+# Index elements in `a` as follows:
+
+a[1, 1]
+
+#-
+
+a[2, :]
+
 # Create an n-dimensional variable $x \in {R}^n$ with bounds $l \le x \le u$
 # ($l, u \in {R}^n$) as follows:
 
@@ -344,6 +352,40 @@ u = [10, 11, 12, 13, 14, 15, 16, 17, 18, 19];
 
 @variable(model, w[1:5, ["red", "blue"]] <= 1)
 
+# Index elements in a `DenseAxisArray` as follows:
+
+z[2, 1]
+
+#-
+
+w[2:3, ["red", "blue"]]
+
+# If all axes are named, you can use keyword indexing for extra readability:
+
+z[i = 2, j = :]
+
+# If names are omitted, an error is thrown:
+
+try                         #hide
+    w[i = 1, j = "red"]
+catch err                   #hide
+    showerror(stderr, err)  #hide
+end                         #hide
+
+# !!! warning
+#     Keyword indexing does not work for `Array`, so `x[i = 1]` will throw an
+#     error.
+
+# As a work-around, pass `DenseAxisArray` to the `container` keyword.
+
+@variable(model, a_dense[i = 1:2, j = 1:2], container = DenseAxisArray)
+
+#-
+
+a_dense[i = 1, j = 2]
+
+# See [Forcing the container type](@ref variable_forcing) for more details.
+
 # #### SparseAxisArrays
 
 # `SparseAxisArrays` are created when the indices do not form a Cartesian product.
@@ -358,6 +400,18 @@ u = [10, 11, 12, 13, 14, 15, 16, 17, 18, 19];
 
 @variable(model, v[i = 1:9; mod(i, 3) == 0])
 
+# Index elements in a `DenseAxisArray` as follows:
+
+u[1, 2]
+
+#-
+
+v[[3, 6]]
+
+# If all axes are named, you can use keyword indexing for extra readability:
+
+v[i = 3]
+
 # ### Integrality
 
 # JuMP can create binary and integer variables. Binary variables are constrained