Most shaping (on a sweater knitted in pieces, like the one above) is approached in the same way, although the resulting action will very much depend on a type of cable.
There are many types of cables out there, from the most traditional vertical rope panel, to some
complex looking intertwined all-over patterns. Therefore, first of all, you'd want to look at the cable pattern (having a chart always helps here, although not strictly necessary), and identify the cables and their repeat. In the photo above, there are very obviously two cable patterns used: the centre panel is a vertical rope that's been mirrored to reflect itself; and the side panel is a honeycomb stitch that repeats itself a number of times.
The only thing to remember when shaping cabled fabric is that you need to keep the flow of the pattern going across your fabric as far as the stitch count would let you. Make them extend as close to the edge as you can. It's always a good idea to separate pattern repeats with markers. Once a few stitches have been decreased or bound off at the edge of the fabric, you will have a partial repeat with a number of stitches that's not quite enough to make a complete cable at that edge. Those edge stitches should be replaced with either knit or purl stitches, always following the established pattern.
Looking at the chart below you'll see that a pattern repeat, highlighted with a red border, is 8 stitches wide and 8 rows tall. To separate a repeat here, you'll need to place a marker 8 stitches away from the edge, marking off a complete repeat. Once the stitches in this repeat have been bound off or decreased you'll need to place another marker, 8 stitches away from the first one, again marking off the following repeat.
Be it a neckline or an armhole, we know that the shaping often spreads across a number of pattern repeats. I am going for a dramatically rounded example here, but the same theory should be applied to any shaping. It isn't the one used in the actual pattern, but for illustration purposes it'll give us a couple of different options to review.
What you can see from looking at the background closely is that this shaping here leaves us with a couple of partial repeats and partial cables to deal with.
These are the 'leftover' partial repeats' stitches that need to be replaced with the background pattern. Since the honeycomb pattern is worked using only the knit stitches, they need to be replaced with plain stocking stitch.
Sometimes, however, a pattern repeat can be broken down into smaller units, with each cable cross being a unit in a repeat. And this would be exactly the case where 'you can keep the flow of the pattern going across your fabric, as far as the stitch count would let you'.
It most certainly can be done here because each cable cross only needs 4 stitches to be completed.
Below, you'll see the leftover stitches in partial repeats highlighted in amber.
On Row 9, a cable cross can be worked, because we still have enough stitches to complete it there.
On Rows 13 and 17, however, there aren't enough stitches for a cable cross and it is a straight forward replacement.
- Mark off a couple of edge repeats on either side of the piece and shift those markers inwards when needed.
- Check if a repeat consists of smaller cable units. Work those stitches in pattern as far as possible, replace remainder of stitches with background.
- If all else fails, chart the shaping following written instructions on graph paper, highlighting any partial repeats. Then go over step 2 following your charted shaping.
don't forget to pin this for later!