The phrase "are difficult to generate" is correct and usable in written English.
You can use it when discussing the challenges or complexities involved in creating something, such as ideas, data, or content.
Example: "New algorithms for data analysis are difficult to generate, requiring extensive research and testing."
Alternatives: "are hard to produce" or "are challenging to create."
"They are difficult to generate and difficult to maintain".
For many problems, comparison functions are difficult to generate, so that the question arises as to an alternative approach.
In severe disease, cross-sectional images of the plaques are difficult to generate because of calcium shadowing or reverberations [10].
These PDX programs are difficult to generate, costly to run and maintain, and must be able to change dynamically in line with technological and scientific advances.
Although AGB is an important variable for evaluating ecosystem function and structure across the landscape, such estimates are difficult to generate without high-resolution satellite data.
For in the ANN (Artificial Neural Networks) method, the training samples are difficult to generate, while combining the linear regression method with ANN method this problem can be solved perfectly.
Generally, it is difficult to generate a connected random graph with a very low average degree, because a sparser graph has a lower possibility of being connected.
He says it is difficult to generate interest beyond those opposed to building on sites such as the one his campaign opposes at Pennbury, near Leicester.
One of the problems we have in England is that it is difficult to generate a sense of belonging in this way.
The media needs a news peg, and when an artist isn't releasing music, or performing, or maintaining the brand, it's difficult to generate interest.
It's estimated that the world needs an extra three trillion dollars to fund the sustainable development goals, which will be difficult to generate without the involvement of the private sector.
