I am new in coding with the Mathcad. I am trying to code a model related to civil engineering (geotechnical engineering), but I have faced several problems. I think the problem is not that much hard, but I couldn't solve it. I wonder If somebody could take a look at it and give me some hints about that. I have attached my file as well as the picture of what I am trying to code.
Thanks in advance.
You're using a variable eta with a subscript i-1. This means that eta must be defined AND must be an array.
Well eta is defined, and is an array PROVIDED that the if-statement (at the top of above picture) is true. Apparently that is not (always) the case.
Either make sure that the if-statement is executed, or provide some other way of generating the eta array, or find a way to execute the 'otherwise' without needing the eta array.
Before continuing, I would recommend you to use the units of measure for all physical quantities present in the worksheet, both constant and variable. In this way they are highlighted inconsistencies that, without such use, would not appear.