I need to label contour lines in QGIS 2.14. I've tried a few things, including Choosing only one contour line to label in QGIS? but it labels with the IDs instead of altitude.
EDIT: I've created the contour lines using this method : loaded an MNT (RGEALTI from IGN in France that contains altitude data), then menu raster / extraction / contour Here's the MNT image:
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EDIT: I went again through the process of extracting contour lines (raster/extraction/contour lines) but this time I added a name to the attribute as suggested below by Gabriel C. And there is an error during the process. Here's the attribute table of the layer: