diff --git a/nnpdf31_proc/NNPDF_POS_ANTI_DOWN_40/metadata.txt b/nnpdf31_proc/NNPDF_POS_ANTI_DOWN_40/metadata.txt
new file mode 100644
index 00000000..d2058577
--- /dev/null
+++ b/nnpdf31_proc/NNPDF_POS_ANTI_DOWN_40/metadata.txt
@@ -0,0 +1,10 @@
+description=Anti-down quark positivity
+x1_label=Q2
+x1_label_tex=$Q^2$
+x1_unit=GeV^2
+x2_label=x
+x2_label_tex=$x$
+x2_unit=
+y_label=xfx
+y_label_tex=$xf(x)$
+y_unit=
diff --git a/nnpdf31_proc/NNPDF_POS_ANTI_DOWN_40/positivity.yaml b/nnpdf31_proc/NNPDF_POS_ANTI_DOWN_40/positivity.yaml
new file mode 100644
index 00000000..9cab05d8
--- /dev/null
+++ b/nnpdf31_proc/NNPDF_POS_ANTI_DOWN_40/positivity.yaml
@@ -0,0 +1,25 @@
+hadron_pid: 2212
+lepton_pid: 11
+pid: -1
+q2: 5.0
+xgrid:
+  - 4.9999999999999998e-07
+  - 1.9407667236782136e-06
+  - 7.5331509514733370e-06
+  - 2.9240177382128657e-05
+  - 1.1349672651536727e-04
+  - 4.4054134013486355e-04
+  - 1.7099759466766963e-03
+  - 6.6373288312005724e-03
+  - 2.5763013859408150e-02
+  - 1.0000000000000001e-01
+  - 1.7999999999999999e-01
+  - 2.6000000000000001e-01
+  - 3.3999999999999997e-01
+  - 4.2000000000000004e-01
+  - 5.0000000000000000e-01
+  - 5.7999999999999996e-01
+  - 6.6000000000000003e-01
+  - 7.3999999999999999e-01
+  - 8.1999999999999995e-01
+  - 9.0000000000000002e-01
diff --git a/nnpdf31_proc/NNPDF_POS_ANTI_STRANGE_40/metadata.txt b/nnpdf31_proc/NNPDF_POS_ANTI_STRANGE_40/metadata.txt
new file mode 100644
index 00000000..f6fd0349
--- /dev/null
+++ b/nnpdf31_proc/NNPDF_POS_ANTI_STRANGE_40/metadata.txt
@@ -0,0 +1,10 @@
+description=Anti-strange quark positivity
+x1_label=Q2
+x1_label_tex=$Q^2$
+x1_unit=GeV^2
+x2_label=x
+x2_label_tex=$x$
+x2_unit=
+y_label=xfx
+y_label_tex=$xf(x)$
+y_unit=
diff --git a/nnpdf31_proc/NNPDF_POS_ANTI_STRANGE_40/positivity.yaml b/nnpdf31_proc/NNPDF_POS_ANTI_STRANGE_40/positivity.yaml
new file mode 100644
index 00000000..b43cdd24
--- /dev/null
+++ b/nnpdf31_proc/NNPDF_POS_ANTI_STRANGE_40/positivity.yaml
@@ -0,0 +1,25 @@
+hadron_pid: 2212
+lepton_pid: 11
+pid: -3
+q2: 5.0
+xgrid:
+  - 4.9999999999999998e-07
+  - 1.9407667236782136e-06
+  - 7.5331509514733370e-06
+  - 2.9240177382128657e-05
+  - 1.1349672651536727e-04
+  - 4.4054134013486355e-04
+  - 1.7099759466766963e-03
+  - 6.6373288312005724e-03
+  - 2.5763013859408150e-02
+  - 1.0000000000000001e-01
+  - 1.7999999999999999e-01
+  - 2.6000000000000001e-01
+  - 3.3999999999999997e-01
+  - 4.2000000000000004e-01
+  - 5.0000000000000000e-01
+  - 5.7999999999999996e-01
+  - 6.6000000000000003e-01
+  - 7.3999999999999999e-01
+  - 8.1999999999999995e-01
+  - 9.0000000000000002e-01
diff --git a/nnpdf31_proc/NNPDF_POS_ANTI_UP_40/metadata.txt b/nnpdf31_proc/NNPDF_POS_ANTI_UP_40/metadata.txt
new file mode 100644
index 00000000..b30bff90
--- /dev/null
+++ b/nnpdf31_proc/NNPDF_POS_ANTI_UP_40/metadata.txt
@@ -0,0 +1,10 @@
+description=Anti-up quark positivity
+x1_label=Q2
+x1_label_tex=$Q^2$
+x1_unit=GeV^2
+x2_label=x
+x2_label_tex=$x$
+x2_unit=
+y_label=xfx
+y_label_tex=$xf(x)$
+y_unit=
diff --git a/nnpdf31_proc/NNPDF_POS_ANTI_UP_40/positivity.yaml b/nnpdf31_proc/NNPDF_POS_ANTI_UP_40/positivity.yaml
new file mode 100644
index 00000000..afd7be39
--- /dev/null
+++ b/nnpdf31_proc/NNPDF_POS_ANTI_UP_40/positivity.yaml
@@ -0,0 +1,25 @@
+hadron_pid: 2212
+lepton_pid: 11
+pid: -2
+q2: 5.0
+xgrid:
+  - 4.9999999999999998e-07
+  - 1.9407667236782136e-06
+  - 7.5331509514733370e-06
+  - 2.9240177382128657e-05
+  - 1.1349672651536727e-04
+  - 4.4054134013486355e-04
+  - 1.7099759466766963e-03
+  - 6.6373288312005724e-03
+  - 2.5763013859408150e-02
+  - 1.0000000000000001e-01
+  - 1.7999999999999999e-01
+  - 2.6000000000000001e-01
+  - 3.3999999999999997e-01
+  - 4.2000000000000004e-01
+  - 5.0000000000000000e-01
+  - 5.7999999999999996e-01
+  - 6.6000000000000003e-01
+  - 7.3999999999999999e-01
+  - 8.1999999999999995e-01
+  - 9.0000000000000002e-01
diff --git a/nnpdf31_proc/NNPDF_POS_CHARM_40/metadata.txt b/nnpdf31_proc/NNPDF_POS_CHARM_40/metadata.txt
new file mode 100644
index 00000000..d09c5f93
--- /dev/null
+++ b/nnpdf31_proc/NNPDF_POS_CHARM_40/metadata.txt
@@ -0,0 +1,10 @@
+description=Charm quark positivity
+x1_label=Q2
+x1_label_tex=$Q^2$
+x1_unit=GeV^2
+x2_label=x
+x2_label_tex=$x$
+x2_unit=
+y_label=xfx
+y_label_tex=$xf(x)$
+y_unit=
diff --git a/nnpdf31_proc/NNPDF_POS_CHARM_40/positivity.yaml b/nnpdf31_proc/NNPDF_POS_CHARM_40/positivity.yaml
new file mode 100644
index 00000000..fdee4a31
--- /dev/null
+++ b/nnpdf31_proc/NNPDF_POS_CHARM_40/positivity.yaml
@@ -0,0 +1,25 @@
+hadron_pid: 2212
+lepton_pid: 11
+pid: 4
+q2: 5.0
+xgrid:
+  - 4.9999999999999998e-07
+  - 1.9407667236782136e-06
+  - 7.5331509514733370e-06
+  - 2.9240177382128657e-05
+  - 1.1349672651536727e-04
+  - 4.4054134013486355e-04
+  - 1.7099759466766963e-03
+  - 6.6373288312005724e-03
+  - 2.5763013859408150e-02
+  - 1.0000000000000001e-01
+  - 1.7999999999999999e-01
+  - 2.6000000000000001e-01
+  - 3.3999999999999997e-01
+  - 4.2000000000000004e-01
+  - 5.0000000000000000e-01
+  - 5.7999999999999996e-01
+  - 6.6000000000000003e-01
+  - 7.3999999999999999e-01
+  - 8.1999999999999995e-01
+  - 9.0000000000000002e-01
diff --git a/nnpdf31_proc/NNPDF_POS_DOWN_40/metadata.txt b/nnpdf31_proc/NNPDF_POS_DOWN_40/metadata.txt
new file mode 100644
index 00000000..173d291e
--- /dev/null
+++ b/nnpdf31_proc/NNPDF_POS_DOWN_40/metadata.txt
@@ -0,0 +1,10 @@
+description=Down quark positivity
+x1_label=Q2
+x1_label_tex=$Q^2$
+x1_unit=GeV^2
+x2_label=x
+x2_label_tex=$x$
+x2_unit=
+y_label=xfx
+y_label_tex=$xf(x)$
+y_unit=
diff --git a/nnpdf31_proc/NNPDF_POS_DOWN_40/positivity.yaml b/nnpdf31_proc/NNPDF_POS_DOWN_40/positivity.yaml
new file mode 100644
index 00000000..3d8901c7
--- /dev/null
+++ b/nnpdf31_proc/NNPDF_POS_DOWN_40/positivity.yaml
@@ -0,0 +1,25 @@
+hadron_pid: 2212
+lepton_pid: 11
+pid: 1
+q2: 5.0
+xgrid:
+  - 4.9999999999999998e-07
+  - 1.9407667236782136e-06
+  - 7.5331509514733370e-06
+  - 2.9240177382128657e-05
+  - 1.1349672651536727e-04
+  - 4.4054134013486355e-04
+  - 1.7099759466766963e-03
+  - 6.6373288312005724e-03
+  - 2.5763013859408150e-02
+  - 1.0000000000000001e-01
+  - 1.7999999999999999e-01
+  - 2.6000000000000001e-01
+  - 3.3999999999999997e-01
+  - 4.2000000000000004e-01
+  - 5.0000000000000000e-01
+  - 5.7999999999999996e-01
+  - 6.6000000000000003e-01
+  - 7.3999999999999999e-01
+  - 8.1999999999999995e-01
+  - 9.0000000000000002e-01
diff --git a/nnpdf31_proc/NNPDF_POS_GLUON_40/metadata.txt b/nnpdf31_proc/NNPDF_POS_GLUON_40/metadata.txt
new file mode 100644
index 00000000..49a0dc72
--- /dev/null
+++ b/nnpdf31_proc/NNPDF_POS_GLUON_40/metadata.txt
@@ -0,0 +1,10 @@
+description=Gluon positivity
+x1_label=Q2
+x1_label_tex=$Q^2$
+x1_unit=GeV^2
+x2_label=x
+x2_label_tex=$x$
+x2_unit=
+y_label=xfx
+y_label_tex=$xf(x)$
+y_unit=
diff --git a/nnpdf31_proc/NNPDF_POS_GLUON_40/positivity.yaml b/nnpdf31_proc/NNPDF_POS_GLUON_40/positivity.yaml
new file mode 100644
index 00000000..e2316324
--- /dev/null
+++ b/nnpdf31_proc/NNPDF_POS_GLUON_40/positivity.yaml
@@ -0,0 +1,25 @@
+hadron_pid: 2212
+lepton_pid: 11
+pid: 21
+q2: 5.0
+xgrid:
+  - 4.9999999999999998e-07
+  - 1.9407667236782136e-06
+  - 7.5331509514733370e-06
+  - 2.9240177382128657e-05
+  - 1.1349672651536727e-04
+  - 4.4054134013486355e-04
+  - 1.7099759466766963e-03
+  - 6.6373288312005724e-03
+  - 2.5763013859408150e-02
+  - 1.0000000000000001e-01
+  - 1.7999999999999999e-01
+  - 2.6000000000000001e-01
+  - 3.3999999999999997e-01
+  - 4.2000000000000004e-01
+  - 5.0000000000000000e-01
+  - 5.7999999999999996e-01
+  - 6.6000000000000003e-01
+  - 7.3999999999999999e-01
+  - 8.1999999999999995e-01
+  - 9.0000000000000002e-01
diff --git a/nnpdf31_proc/NNPDF_POS_STRANGE_40/metadata.txt b/nnpdf31_proc/NNPDF_POS_STRANGE_40/metadata.txt
new file mode 100644
index 00000000..8128fd74
--- /dev/null
+++ b/nnpdf31_proc/NNPDF_POS_STRANGE_40/metadata.txt
@@ -0,0 +1,10 @@
+description=Strange quark positivity
+x1_label=Q2
+x1_label_tex=$Q^2$
+x1_unit=GeV^2
+x2_label=x
+x2_label_tex=$x$
+x2_unit=
+y_label=xfx
+y_label_tex=$xf(x)$
+y_unit=
diff --git a/nnpdf31_proc/NNPDF_POS_STRANGE_40/positivity.yaml b/nnpdf31_proc/NNPDF_POS_STRANGE_40/positivity.yaml
new file mode 100644
index 00000000..d42357a8
--- /dev/null
+++ b/nnpdf31_proc/NNPDF_POS_STRANGE_40/positivity.yaml
@@ -0,0 +1,25 @@
+hadron_pid: 2212
+lepton_pid: 11
+pid: 3
+q2: 5.0
+xgrid:
+  - 4.9999999999999998e-07
+  - 1.9407667236782136e-06
+  - 7.5331509514733370e-06
+  - 2.9240177382128657e-05
+  - 1.1349672651536727e-04
+  - 4.4054134013486355e-04
+  - 1.7099759466766963e-03
+  - 6.6373288312005724e-03
+  - 2.5763013859408150e-02
+  - 1.0000000000000001e-01
+  - 1.7999999999999999e-01
+  - 2.6000000000000001e-01
+  - 3.3999999999999997e-01
+  - 4.2000000000000004e-01
+  - 5.0000000000000000e-01
+  - 5.7999999999999996e-01
+  - 6.6000000000000003e-01
+  - 7.3999999999999999e-01
+  - 8.1999999999999995e-01
+  - 9.0000000000000002e-01
diff --git a/nnpdf31_proc/NNPDF_POS_UP_40/metadata.txt b/nnpdf31_proc/NNPDF_POS_UP_40/metadata.txt
new file mode 100644
index 00000000..64bdc173
--- /dev/null
+++ b/nnpdf31_proc/NNPDF_POS_UP_40/metadata.txt
@@ -0,0 +1,10 @@
+description=Up-quark positivity
+x1_label=Q2
+x1_label_tex=$Q^2$
+x1_unit=GeV^2
+x2_label=x
+x2_label_tex=$x$
+x2_unit=
+y_label=xfx
+y_label_tex=$xf(x)$
+y_unit=
diff --git a/nnpdf31_proc/NNPDF_POS_UP_40/positivity.yaml b/nnpdf31_proc/NNPDF_POS_UP_40/positivity.yaml
new file mode 100644
index 00000000..e5646a9e
--- /dev/null
+++ b/nnpdf31_proc/NNPDF_POS_UP_40/positivity.yaml
@@ -0,0 +1,25 @@
+hadron_pid: 2212
+lepton_pid: 11
+pid: 2
+q2: 5.0
+xgrid:
+  - 4.9999999999999998e-07
+  - 1.9407667236782136e-06
+  - 7.5331509514733370e-06
+  - 2.9240177382128657e-05
+  - 1.1349672651536727e-04
+  - 4.4054134013486355e-04
+  - 1.7099759466766963e-03
+  - 6.6373288312005724e-03
+  - 2.5763013859408150e-02
+  - 1.0000000000000001e-01
+  - 1.7999999999999999e-01
+  - 2.6000000000000001e-01
+  - 3.3999999999999997e-01
+  - 4.2000000000000004e-01
+  - 5.0000000000000000e-01
+  - 5.7999999999999996e-01
+  - 6.6000000000000003e-01
+  - 7.3999999999999999e-01
+  - 8.1999999999999995e-01
+  - 9.0000000000000002e-01
diff --git a/runcardsrunner/cli/run.py b/runcardsrunner/cli/run.py
index a3475dd7..93e7b44a 100644
--- a/runcardsrunner/cli/run.py
+++ b/runcardsrunner/cli/run.py
@@ -7,7 +7,7 @@
 import yaml
 
 from .. import install, log, table, tools
-from ..external import mg5, yad
+from ..external import mg5, positivity, yad
 from ._base import command
 
 
@@ -62,11 +62,17 @@ def main(dataset, theory, pdf):
     rich.print(dataset)
 
     if yad.is_dis(dataset):
-        rich.print(f"Computing [red]{dataset}[/]...")
-        runner = yad.Yadism(dataset, theory, pdf, timestamp=timestamp)
+        color = "red"
+        external = yad.Yadism
+    elif positivity.is_positivity(dataset):
+        color = "yellow"
+        external = positivity.Positivity
     else:
-        rich.print(f"Computing [blue]{dataset}[/]...")
-        runner = mg5.Mg5(dataset, theory, pdf, timestamp=timestamp)
+        color = "blue"
+        external = mg5.Mg5
+
+    rich.print(f"Computing [{color}]{dataset}[/]...")
+    runner = external(dataset, theory, pdf, timestamp=timestamp)
 
     install_reqs(runner, pdf)
     run_dataset(runner)
diff --git a/runcardsrunner/external/positivity.py b/runcardsrunner/external/positivity.py
new file mode 100644
index 00000000..985ae79e
--- /dev/null
+++ b/runcardsrunner/external/positivity.py
@@ -0,0 +1,96 @@
+# -*- coding: utf-8 -*-
+import json
+
+import lhapdf
+import numpy as np
+import pandas as pd
+import pineappl
+import yaml
+
+from .. import paths
+from . import interface
+
+
+def is_positivity(name):
+    """
+    Is this a positivity dataset?
+
+    The decision is based on the existance of the `positivity.yaml` file.
+
+    Parameters
+    ----------
+        name : str
+            dataset name
+    """
+    return (paths.runcards / name / "positivity.yaml").exists()
+
+
+class Positivity(interface.External):
+    def __init__(self, *args, **kwargs):
+        super().__init__(*args, **kwargs)
+
+    def run(self):
+        with open(paths.runcards / self.name / "positivity.yaml") as o:
+            self.runcard = yaml.safe_load(o)
+
+    def generate_pineappl(self):
+        self.xgrid = self.runcard['xgrid']
+        self.lepton_pid = self.runcard['lepton_pid']
+        self.pid = self.runcard['pid']
+        self.q2 = self.runcard['q2']
+        self.hadron_pid = self.runcard['hadron_pid']
+
+        # init pineappl objects
+        lumi_entries = [pineappl.lumi.LumiEntry([(self.pid, self.lepton_pid, 1.0)])]
+        orders = [pineappl.grid.Order(0, 0, 0, 0)]
+        bins = len(self.xgrid)
+        bin_limits = list(map(float, range(0, bins + 1)))
+        # subgrid params - default is just sufficient
+        params = pineappl.subgrid.SubgridParams()
+        # inti grid
+        grid = pineappl.grid.Grid.create(lumi_entries, orders, bin_limits, params)
+        limits = []
+        # add each point as a bin
+        for bin_, x in enumerate(self.xgrid):
+            # keep DIS bins
+            limits.append((self.q2, self.q2))
+            limits.append((x, x))
+            # delta function
+            array = np.zeros(len(self.xgrid))
+            array[bin_] = x
+            # create and set
+            subgrid = pineappl.import_only_subgrid.ImportOnlySubgridV1(
+                array[np.newaxis, :, np.newaxis],
+                [self.q2],
+                self.xgrid,
+                [1.0],
+            )
+            grid.set_subgrid(0, bin_, 0, subgrid)
+        # set the correct observables
+        normalizations = [1.0] * bins
+        remapper = pineappl.bin.BinRemapper(normalizations, limits)
+        grid.set_remapper(remapper)
+
+        # set the initial state PDF ids for the grid
+        grid.set_key_value("initial_state_1", str(self.hadron_pid))
+        grid.set_key_value("initial_state_2", str(self.lepton_pid))
+        grid.set_key_value("runcard", json.dumps(self.runcard))
+        grid.set_key_value("lumi_id_types", "pdg_mc_ids")
+        grid.optimize()
+        grid.write(str(self.grid))
+
+
+    def results(self):
+        pdf = lhapdf.mkPDF(self.pdf)
+        d = {
+            'result': [pdf.xfxQ2(self.pid, x, self.q2) for x in self.xgrid],
+            'error': [1e-15] * len(self.xgrid),
+            'sv_min': [np.amin([pdf.xfxQ2(self.pid, x, 0.25 * self.q2), pdf.xfxQ2(self.pid, x, self.q2), pdf.xfxQ2(self.pid, x, 4.0 * self.q2)]) for x in self.xgrid],
+            'sv_max': [np.amax([pdf.xfxQ2(self.pid, x, 0.25 * self.q2), pdf.xfxQ2(self.pid, x, self.q2), pdf.xfxQ2(self.pid, x, 4.0 * self.q2)]) for x in self.xgrid],
+        }
+        results = pd.DataFrame(data=d)
+
+        return results
+
+    def collect_versions(self):
+        return {}
diff --git a/runcardsrunner/table.py b/runcardsrunner/table.py
index 3a279d24..3a988727 100644
--- a/runcardsrunner/table.py
+++ b/runcardsrunner/table.py
@@ -65,7 +65,7 @@ def print_table(pineappl_results, external_results, dest):
     comparison["PineAPPL"] = pineappl_results["integ"]
     comparison["MC"] = external_results["result"]
     comparison["sigma 1/100"] = (
-        external_results["error"] / external_results["result"] * 1e2
+        external_results["error"] / abs(external_results["result"]) * 1e2
     )
 
     # ratios