you might like https://omrelli.ug/g9/ which is a similar concept but for graphics
Show HN: I made a spreadsheet where formulas also update backwards
11–20 of 122 posts
Re: Show HN: I made a spreadsheet where formulas also update backwards
#12you might like https://omrelli.ug/g9/ which is a similar concept but for graphics
I do like g9! It was a strong inspiration for bidicalc actually!
Re: Show HN: I made a spreadsheet where formulas also update backwards
#13This is really cool! It's like Excel's goal seek but can also handle the case of arbitrary input cells. Goal seeek can only handle one input and one output cell.
But how do you handle the case where multiple variables can be changed? If multiple input cells is the key difference from Goal seek, i think some more rigor should be placed into the algorithm here
e.g. setting A1 + B1 and wanting the result to be 5. Currently it bumps both A1 and B1 equally. What's the thought process behind this?
Re: Show HN: I made a spreadsheet where formulas also update backwards
#14LOL! Gemini suggested to implement this to me literally yesterday: bidirectional computations.
The example was that given a temperature in Celsius and Fahrenheit, modifying either of them should update their counterpart.
In angular that would be two linked signals for instance, but even that is a bit fringe. Gemini was going for something even more elaborated.
I told Gemini that spreadsheets were actually not doing that and that I had ways to implement that behavior without the complexity.
Just writing that to show the rabbit hole people are going to fall into if they let their llms go brrr. ;D
In any case, the problem is interesting. The point was to include bi-directionality inside a graph of computations so that we didn't get bogged down by cycles. The benefit being that it would handle float precision issues.
My more manual solution expect that floats precision issues are handled explicitly. I think that this level of explicitness is needed anyway for proper floating point error mitigation.
Re: Show HN: I made a spreadsheet where formulas also update backwards
#15In Excel you have goal seek for this functionality. I believe it does some form of numerical solving of the equation system.
Good for every situation when you need to solve equations!
In the context of using spreadsheets I think about solving simple financial or maybe construction/mechanical design problems where you don’t want to solve it manually or program it and a spreadsheet is a quick and useful interface.
Re: Show HN: I made a spreadsheet where formulas also update backwards
#16Hm? I don't get it. What's the point of calculating backwards non-invertible operations such as addition? Isn't the result just arbitrary?
I made this mostly as a fun challenge :) You are right that there is some arbitrariness involved when picking a solution, however it's a bit more subtle than that. Let's say our problem has N free variables. Step 1 is finding the subset of R^N that is the solution to the root finding problem. If this subset is a point, we are done (return that point). Note that if there is no solution at all bidicalc should correctly…
does the algorithm tries to make minimal changes to the free variables ?
If we have 1 + 1 = 2 and change 2 -> 4 then -100000 + 100004 = 4 is also a valid solution.
When I tried it it changed it to 2 + 2 so perhaps there is optimization but also a valid optimization can be minimal free variable changes in which case it would be 1+3 = 4 and we update 1 free variable instead of 2.
I have no idea which is better just curios how it works.
I like the idea very much.
Re: Show HN: I made a spreadsheet where formulas also update backwards
#17[deleted]
Re: Show HN: I made a spreadsheet where formulas also update backwards
#18This is really cool! It's like Excel's goal seek but can also handle the case of arbitrary input cells. Goal seeek can only handle one input and one output cell. But how do you handle the case where multiple variables can be changed? If multiple input cells is the key difference from Goal seek, i think some more rigor should be placed into the algorithm here e.g. setting A1 + B1 and wanting the result to be 5. Curren…
Yeah. The UI could have a lock icon to set, eg B1 should stay fixed and then only A1 would change.
Re: Show HN: I made a spreadsheet where formulas also update backwards
#19This is really cool! It's like Excel's goal seek but can also handle the case of arbitrary input cells. Goal seeek can only handle one input and one output cell. But how do you handle the case where multiple variables can be changed? If multiple input cells is the key difference from Goal seek, i think some more rigor should be placed into the algorithm here e.g. setting A1 + B1 and wanting the result to be 5. Curren…
Yeah. The UI could have a lock icon to set, eg B1 should stay fixed and then only A1 would change.
It supports this. If you type # before a number, like #5, it's made constant.
Re: Show HN: I made a spreadsheet where formulas also update backwards
#20interesting. like Excel Solver? or OpenSolver, Gurobi, other optimizers? or different objective?