diff --git a/exercise7/Makefile b/exercise7/Makefile
index 690b227..b14a03b 100644
--- a/exercise7/Makefile
+++ b/exercise7/Makefile
@@ -18,13 +18,16 @@ images/%.png: data/%.dat
 	./plot_image.sh $<
 movie: ${IMAGES}
 	ffmpeg -y -an -i images/%5d.png -vcodec libx264 -pix_fmt yuv420p -profile:v baseline -level 3 -r 12 wave.mp4
-check: dirs sequential parallel
+data: dirs sequential parallel
 	mkdir -p data_sequential
 	./sequential
 	cp -rf ./data/* ./data_sequential
 	./parallel
-	python3 compare.py data_sequential/00000.dat data/00000.dat
-	python3 compare.py data_sequential/00075.dat data/00075.dat
-	rm -rf data_sequential
+compare/%: data
+	python3 compare.py data_sequential/$(shell printf "%05d" $*).dat data/$(shell printf "%05d" $*).dat
+diff/%: data
+	python3 plot_differences.py data_sequential/$(shell printf "%05d" $*).dat data/$(shell printf "%05d" $*).dat
+check: compare/0 compare/75
 clean:
 	-rm -fr sequential parallel data images wave.mp4
+	rm -rf data_sequential
diff --git a/flake.nix b/flake.nix
index c262d49..0d5f3f5 100644
--- a/flake.nix
+++ b/flake.nix
@@ -53,6 +53,7 @@
           binutils
           uv
           python3Packages.numpy
+          python3Packages.matplotlib
         ];
         shellHook = ''
           echo welcome!