ENH,TST: Add symbol to _repr_latex_.

 * Add tests for symbol in TestLatexRepr

numpy/polynomial/_polybase.py

@@ -438,18 +438,18 @@ def _repr_latex_(self):
         # get the scaled argument string to the basis functions
         off, scale = self.mapparms()
         if off == 0 and scale == 1:
-            term = 'x'
+            term = self.symbol
             needs_parens = False
         elif scale == 1:
-            term = f"{self._repr_latex_scalar(off)} + x"
+            term = f"{self._repr_latex_scalar(off)} + {self.symbol}"
             needs_parens = True
         elif off == 0:
-            term = f"{self._repr_latex_scalar(scale)}x"
+            term = f"{self._repr_latex_scalar(scale)}{self.symbol}"
             needs_parens = True
         else:
             term = (
                 f"{self._repr_latex_scalar(off)} + "
-                f"{self._repr_latex_scalar(scale)}x"
+                f"{self._repr_latex_scalar(scale)}{self.symbol}"
             )
             needs_parens = True
 
@@ -485,7 +485,7 @@ def _repr_latex_(self):
             # in case somehow there are no coefficients at all
             body = '0'
 
-        return rf"$x \mapsto {body}$"
+        return rf"${self.symbol} \mapsto {body}$"
 
 
 

numpy/polynomial/tests/test_printing.py

@@ -419,3 +419,24 @@ def test_multichar_basis_func(self):
         p = poly.HermiteE([1, 2, 3])
         assert_equal(self.as_latex(p),
             r'$x \mapsto 1.0\,{He}_{0}(x) + 2.0\,{He}_{1}(x) + 3.0\,{He}_{2}(x)$')
+
+    def test_symbol_basic(self):
+        # default input
+        p = poly.Polynomial([1, 2, 3], symbol='z')
+        assert_equal(self.as_latex(p),
+            r'$z \mapsto 1.0 + 2.0\,z + 3.0\,z^{2}$')
+
+        # translated input
+        p = poly.Polynomial([1, 2, 3], domain=[-2, 0], symbol='z')
+        assert_equal(self.as_latex(p),
+            r'$z \mapsto 1.0 + 2.0\,\left(1.0 + z\right) + 3.0\,\left(1.0 + z\right)^{2}$')
+
+        # scaled input
+        p = poly.Polynomial([1, 2, 3], domain=[-0.5, 0.5], symbol='z')
+        assert_equal(self.as_latex(p),
+            r'$z \mapsto 1.0 + 2.0\,\left(2.0z\right) + 3.0\,\left(2.0z\right)^{2}$')
+
+        # affine input
+        p = poly.Polynomial([1, 2, 3], domain=[-1, 0], symbol='z')
+        assert_equal(self.as_latex(p),
+            r'$z \mapsto 1.0 + 2.0\,\left(1.0 + 2.0z\right) + 3.0\,\left(1.0 + 2.0z\right)^{2}$')