One of the things you're likely to encounter as a knitter, whether you're working in lace, cables, or colorwork, is a repeat-based chart. Some folks don't like knitting from charts all that much and would prefer to work from a pattern where the instructions are written out, which works just fine for many cable or lace patterns, but it's a little tricky to do any colorwork without using a chart. And so I love charts. They are incredibly useful, and with a repeat-based chart, we're able to save lots of space in the written pattern as well.
First thing's first: what is a repeat-based chart? In short, it's a small chart, where each row on the chart is worked a certain number of times per row/round of knitting and the total number of rows on the chart can be repeated as well. We'll start with a simple example, for those who are new to charts:
As you can see, this chart has four rows and four columns which are numbered in the order in which they're knit - that is, you start "reading" the chart at the bottom right, work your way from right to left across the row, then move to the next row above it, again working from right to left. While this feels backwards compared to how we read lines on a page, this is exactly how our stitches line up as we work them, and so this is how we orient the chart.*
When you see a chart like this, which is only 4 stitches wide, and you're working a round that has 40 stitches, you know you're going to be working in a series of repeats. This means you'll knit each row of the 4-stitch repeat 10 times (to fill all 40 stitches) before you move on to the next row of the chart. The best way to visualize this is to take our sample chart and line up 10 repeats side by side:
We can see how 10 repeats of the 4x4 chart adds up to 40 stitches, and it's easier to see how the repeats line up to form the pattern.
A really great example of repeat-based charts in action is my Pine Bough Cowl (rav link - Skacel link -as it's a free pattern, you can download it if you want to see the whole thing). I wanted to use Pine Bough Cowl as an example because I've had a few questions from knitters starting the cowl who were new to this type of chart and weren't sure exactly how to use it (the pattern writing in this particular pattern is pretty bare bones, it must be said).
Here's a look at one of the charts:
The pattern reads:
Chart A: section 1 one time, section 2 three times, section 3 one time.
This relies pretty heavily on knowledge of how the chart works, so I wanted to walk through it step by step. This chart looks a lot like the example shown above, only larger. The biggest difference here, though, is that the chart is broken up into three sections (numbered 1, 2, and 3 on the left side). These are the sections referred to in the pattern text. These sections could effectively be their own individual charts, but they're oriented this way so that you can see how the patterns line up.
Breaking down the pattern instructions, we're told to work section 1 one time. The number of stitches per round for this pattern is 100, and this chart is 10 stitches wide. This means we'll work each row of the chart 10 times per round of knitting. So to work section 1, I would work row 1 of the chart 10 times, row 2 of the chart 10 times, and row 3 of the chart 10 times, for 3 complete rounds. That completes section 1.
Next, we're instructed to work section 2 three times. This works just like section 1, except that when we finish section 2 we go back to the first row of section 2 of the chart (row 4). We do this until we have worked all 10 rounds of section 2 three times. (So working section 2 three times means working 30 rounds of knitting).
Lastly, for Chart A, we work section 3 one time. The first row of section 3 of the chart (row 14) gets worked 10 times to fill the round, then the second row of section 3 of the chart gets worked 10 times, and so on and so forth until you have completed section 3.
We can visualize this with some voluminous copy-and-paste usage to line up the actual number of repeats side by side, as we did with the simple example above.
I've left spaces between the repeats (and larger spaces between the sections) so that we don't lose sight of the original chart - for when lined up like this, the pattern takes over - and I've omitted the numbers, but this is essentially a chart that is 100 stitches wide and 43 rows tall, where each box represents a stitch you're actually knitting based on the instructions. I think being able to visualize how a repeat-based chart lines up to create the pattern is a really useful tool in being able to read charts comfortably.
It becomes easy to see why repeat-based charts are useful, as well, when you see how much space the expanded chart would take up!
If you have any questions or experiences with this type of chart, please feel free to share them in the comments.
***A side note for those who download the Pine Bough Cowl pattern: there is an error in the file that Skacel has yet to correct, in the section that follows:
Rep Chart A, Chart B and Stripe Section 2 three times for a total of four times.
This incorrectly omits Stripe Section 1, and so it should read:
Rep Chart A, Stripe Section 1, Chart B, and Stripe Section 2 three times for a total of four times.
* Update: Thanks to Jayne for pointing out in the comments that this is only true if you're knitting the traditional right-handed way; many left-handed knitters typically knit left-to-right, which is often referred to as knitting "backwards." The important point is that the chart mirrors the right-side surface of your knitting, so you want to work the stitches of the chart in the same order as you're actually knitting stitches - working from right-to-left if you're working the traditional right-handed way, or working from left-to-right if you're a lefty or if you just have a liking for knitting in the opposite direction. There's a great Craftsy article on left-handed knitting here.