The phrase "an irregular pattern" is correct and usable in written English.
It can be used when describing something that does not follow a regular or consistent pattern. Example: The artist's painting had an irregular pattern of colors, with splashes and swirls that seemed to have no rhyme or reason.
The staining has an irregular pattern in mutants.
They're becoming more representative, albeit in an irregular pattern, as befits a continent with 54 countries.
Such an irregular pattern might signal the leisurely and unpredictable passage of massive spacecraft in front of the star.
The largest ice field in Europe (excluding Iceland), it is oriented northeast-southwest and extends in an irregular pattern for about 45 miles (75 km).
The RHEED intensity of the first LaO layer shows an irregular pattern, reflecting the state of surface chemistry, charge, and morphology during the transition from TiO2 to LaO.
It is also known that the communications link to Rosetta failed intermittently in an irregular pattern shortly after the landing but always immediately re-established itself.
In contrast to most mammalian species, the ciliary processes in the mouse eye form an irregular pattern.
The result was an irregular pattern of Protestant and Roman Catholic areas, cutting across the boundaries of language and physical geography, which is still in evidence today.
Next door to the Bird's Nest is the Aquatics Center, known as the Water Cube, a rectilinear building with a blue-gray exterior of translucent plastic pillows set in an irregular pattern intended to evoke bubbles.
After someone in the city government noticed an irregular pattern in the payments from the merchants in April, the authorities began investigating Ms. Compoccia, said Patrick Clark, a spokesman for the Department of Investigation.
Since then she has had a grand mal fit - a major seizure - every two weeks and an irregular pattern of petit mals, where her brain appears to briefly cut out, most days.
