Solving mathematical functions made from dashboard inputs

lalo · 2 April 2020 05:31

Hey @zenofmud Paul Thanks it does what i want but is still having a problem when the dropdown options appears on dashboar looks like this:
equation options dropdown
As I understand that is a key object there is a way to change the 0 for example for the name equation sally and the for the 1 equation carl or something like that?
here is the image of the debug
arrayequations

also I have another problem when i reboot my Raspberry my json file with the equations saved are like erased when i try to recover it in the debug appears empty i will put an screenshot and also the flow.
empty

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i<msg.payload.length; i++) {\n    switch (msg.payload[i].type) {\n        case 'undefined': \n            // the global variable probably had no value, nothing needs to be restored\n            output.push(msg.payload[i].key + \" is undefined.\");\n            break;\n        case 'number':\n            if (msg.payload[i].value===\"NaN\") {\n                // there is no valid value to be restored, skip this variable\n                output.push(msg.payload[i].key + \" is NaN.\");\n            } else {\n                if (msg.payload[i].value.toString().indexOf(\".\")>-1) {\n                    // the value appears to be a float\n                    global.set(msg.payload[i].key,parseFloat(msg.payload[i].value));\n                    output.push(msg.payload[i].key + \" is restored to \" + msg.payload[i].value);\n                } else {\n                    global.set(msg.payload[i].key,parseInt(msg.payload[i].value));\n                    output.push(msg.payload[i].key + \" is restored to \" + msg.payload[i].value);\n                }\n            }\n            break;\n        case 'string':\n            global.set(msg.payload[i].key,msg.payload[i].value);\n            output.push(msg.payload[i].key + \" is restored to \" + msg.payload[i].value);\n            break;\n        case 'boolean':\n            global.set(msg.payload[i].key,msg.payload[i].value===\"true\");\n            output.push(msg.payload[i].key + \" is restored to \" + msg.payload[i].value);\n            break;\n    }\n}\n\nmsg.payload = output;\nreturn msg;","outputs":1,"noerr":0,"x":640,"y":400,"wires":[["5bc9e96f.723ff8"]]},{"id":"796ae060.2571d","type":"json","z":"217dd16.38f122e","name":"","x":490,"y":320,"wires":[["3cf22d71.3cf902"]]},{"id":"cc306e1f.95de2","type":"json","z":"217dd16.38f122e","name":"","x":510,"y":400,"wires":[["baebe8d4.f4d4e8"]]},{"id":"5bc9e96f.723ff8","type":"function","z":"217dd16.38f122e","name":"equation restore","func":"msg.topic = \"equa\";\nmsg.payload = global.get(\"equa\");\nreturn msg;","outputs":1,"noerr":0,"x":800,"y":400,"wires":[["e13d9371.87db7"]]},{"id":"41a8df7d.8a1b2","type":"debug","z":"217dd16.38f122e","name":"","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"false","x":850,"y":320,"wires":[]},{"id":"73bebdc6.3a46b4","type":"ui_dropdown","z":"217dd16.38f122e","name":"","label":"","tooltip":"","place":"Select option","group":"679f2509.be684c","order":0,"width":0,"height":0,"passthru":true,"options":[{"label":"","value":"","type":"str"}],"payload":"","topic":"","x":1360,"y":400,"wires":[["810a2cc2.b603c","fda2e215.67a4"]]},{"id":"810a2cc2.b603c","type":"ui_toast","z":"217dd16.38f122e","position":"top right","displayTime":"3","highlight":"","outputs":0,"ok":"OK","cancel":"","topic":"","name":"","x":1570,"y":460,"wires":[]},{"id":"93af67ea.420c68","type":"function","z":"217dd16.38f122e","name":"transform data to correct format","func":"msg.options = [];//create empty array\n    let row = msg.payload; //get the row\n    msg.options.push(row);//add the row to array    \nreturn msg;","outputs":1,"noerr":0,"x":1150,"y":400,"wires":[["73bebdc6.3a46b4"]]},{"id":"fda2e215.67a4","type":"debug","z":"217dd16.38f122e","name":"","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"false","x":1550,"y":340,"wires":[]},{"id":"6114a54b.88c9fc","type":"inject","z":"217dd16.38f122e","name":"","topic":"","payload":"y = 2.1425x + 3.8416 ","payloadType":"str","repeat":"","crontab":"","once":false,"onceDelay":0.1,"x":180,"y":140,"wires":[["8300838.480678"]]},{"id":"33030a2a.bd0b66","type":"inject","z":"217dd16.38f122e","name":"","topic":"","payload":"y = 4.4607x + 8.3455 ","payloadType":"str","repeat":"","crontab":"","once":false,"onceDelay":0.1,"x":180,"y":180,"wires":[["8300838.480678"]]},{"id":"4037b410.2ddfac","type":"inject","z":"217dd16.38f122e","name":"","topic":"","payload":"y = 7.5648x + 13.75","payloadType":"str","repeat":"","crontab":"","once":false,"onceDelay":0.1,"x":170,"y":220,"wires":[["8300838.480678"]]},{"id":"e13d9371.87db7","type":"function","z":"217dd16.38f122e","name":"","func":"var arr = global.get(\"equa\")||[];\nmsg.payload = arr;\nreturn msg;","outputs":1,"noerr":0,"x":950,"y":400,"wires":[["93af67ea.420c68"]]},{"id":"8300838.480678","type":"function","z":"217dd16.38f122e","name":"","func":"if (!context.outputAlarms) {\n   context.outputAlarms = [];\n}\ncontext.outputAlarms.push(msg.payload);\nmsg.payload = context.outputAlarms;\nreturn msg; ","outputs":1,"noerr":0,"x":430,"y":180,"wires":[["71ed98ef.8705c8","6d54e799.eb1b68"]]},{"id":"71ed98ef.8705c8","type":"debug","z":"217dd16.38f122e","name":"","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"false","x":670,"y":180,"wires":[]},{"id":"6d54e799.eb1b68","type":"function","z":"217dd16.38f122e","name":"","func":"var equa = msg.payload;\n\nglobal.set('equa',equa);\n\nreturn msg;","outputs":1,"noerr":0,"x":600,"y":140,"wires":[["31a04691.d2251a"]]},{"id":"31a04691.d2251a","type":"debug","z":"217dd16.38f122e","name":"","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"false","x":770,"y":140,"wires":[]},{"id":"a89a8a34.044418","type":"comment","z":"217dd16.38f122e","name":"equation data in","info":"","x":140,"y":100,"wires":[]},{"id":"679f2509.be684c","type":"ui_group","z":"","name":"Default","tab":"658319a6.10c4d8","disp":true,"width":"6","collapse":false},{"id":"658319a6.10c4d8","type":"ui_tab","z":"","name":"Menu","icon":"fa-tachometer","order":1,"disabled":false,"hidden":false}]

zenofmud · 2 April 2020 09:39

Lalo - why have you added another function numt in the first part? All you need is one function node with the following

var arr = global.get("equa")||[]
arr.push(msg.payload)
global.set('equa',arr)
return msg

Line 1 var arr = global.get("equa")||[] creates a variable 'arr' and the set it to the value of the global variable 'equa' or it that does not exist, it sets it to an empty array
line 2 arr.push(msg.payload) adds what is in msg.payload to the end of the array
line 3 global.set('equa',arr) writes the contents of 'arr' to the global variable 'equa'
line 4 return msg returns the msg

If you want to, you could add msg.payload = arr before the return msg so the debug would show the results in the debug window.

I have another problem when i reboot my Raspberry my json file with the equations saved are like erased

Are you saying that the file on your pi /home/pi/global.json is erased when you reboot? Or you talking about global.equa?

If it is global.equa, have you read the documentation on Working with context? You should read the section on Saving context data to the file-system so if you reboot your pi, the data will be saved.

UPDATE: put a debug node after the 'Restore' function and a second after the 'equation restore' function (both set to display the Complete msg object) and see if you are getting the results you want.

lalo · 2 April 2020 20:48

Are you saying that the file on your pi /home/pi/global.json is erased when you reboot? Or you talking about global.equa ?

No i mean the /home/pi/global.json is not erased but the data inside is erased i'm following your advices thanks.

zenofmud · 2 April 2020 21:31

If the data is being erased then your backup flow is writting empty data to it. Since you tell it to overwrite the file each time. So now you have to determine why is it writing empty data?

If you have not specified (in settings.js) that the context variables should be persistant and you stop/start node red, then they go away. This is probably what is causing the issue.

lalo · 4 April 2020 04:24

@zenofmud @JGKK. Paul and Johannes thank you i read all that you told me and it works how i want, now i'm in the part after selecting my dropdown options and i'm using a case function to make a simple sum but that's just to see how it works so basically i want to do 2 things. The first one i don't know if it's possible to create automatic cases when is added a new equation. For example if i add this ecuation y = 4.4607x + 8.3455 will create a new case and if it is selected i can resolve the ecuation for example if i choose y = 4.4607x + 8.3455 and it appears on the dropdown in a function it substitute the values in x to solve it .
Best regards from Lalo this is my current flow.

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zenofmud · 4 April 2020 07:11

Please explain how you would solve the equation on paper. Give a detailed step by step explanation

lalo · 6 April 2020 04:15

@zenofmud Paul something really simple like this.

solve

zenofmud · 6 April 2020 09:35

Where did x come from? How does the value of x get entered? This is something new that is not shown in the flow at all.

So you are storing a formula as a string. To solve the formula you will first need to parse the string so you know what computation needs to be done.

But before that, you need to validate you have a valid formula? Say someone entered a formula
4.4607x + 8.3455 = y or y = 4.4607x + 8.3455 or there is a typo like y + 4.4607x + 8.3455 or they enter animals equals six dogs added to three cats?

So you figure out
1 - how to validate the text string to see if it is a valid formula when it is entered
2 - how to parse the string formula and create the logic to handle all the cases it could be (is it doing + or - or / etc, could there a number raised to a power?)
3 - where x is coming from
4 - could there be more than one variable for the formula for example y = 4.4607x + 8.3455z

You have your work cut out for you. Feel free to ask questions and provide the code you are having issues with.

lalo · 7 April 2020 05:10

Hi @zenofmud Paul.

I have seen some documentation on excel to validate with some rules. But i just have seen some buttons and commands to see if text or dates are validate.
I think i will only have linear regression because i will have some data from excel and get the equation.
X is coming from a number input on the dashboard
i think i could't be more than one variable.

JGKK · 7 April 2020 05:48

you are building a kind of calculator. I think you will have to build something from ground up that tokenizes your expression string and than validates to things like numbers decimals and operands.
This is not something that is build into nodered or javascript but it can be done.
Search goggle for javascript calculator and you will find many tutorials you can learn from.

lalo · 10 April 2020 04:49

@JGKK i was looking for some kind of calculator and i found this that i think is really close to what i want.

https://www.youtube.com/watch?v=4GCC5DBh_Pk

also i found this code:

//solve linear equations
var x = nerdamer.solve('(x+1)*3=x-6', 'x');
console.log(x.toString());
//quadratic
var x2 = nerdamer.solve('x^2-8x+15', 'x');
console.log(x2.toString());
//quadratic algebraically
var x3 = nerdamer.solve('x^2-ax+3*b', 'x');
console.log(x3.toString());
//multiple roots
var x4 = nerdamer.solve('x^6+41*x^5+652*x^4+5102*x^3+20581*x^2+40361*x+30030', 'x');
console.log(x4.toString());
//functions - numerically around to zero up to a predefined range
var x5 = nerdamer.solve('cos(x)^2+sin(x-1)', 'x');
console.log(x5.toString());
//solve a system of linear equations
var x6 = nerdamer.solveEquations(['2x+y=7', 'x-y+3z=11', 'y-z=-1']);
console.log(x6.toString());
//solve a system of nonlinear equations
var x7 = nerdamer.solveEquations(['3*x^2/y=2', 'z*x*y-1=35', '5*z^2+7=52']);
console.log(x7.toString());

lalo · 10 April 2020 05:04

and also this.

gist.github.com

https://gist.github.com/torjusti/cd66074e4273a6d318af

cas.js

// Prototype that stores information about a given polynomial.
function Polynomial(data) {
  // Support providing already existing Polynomials.
  this.polynomial = data instanceof Polynomial ? data.polynomial : data;
}

// Rank all coefficients in the polynomial and return the largest.
Polynomial.prototype.getLargestCoefficient = function() {
  var re = /(\d+)/g, match, max = 0;
  while(match = re.exec(this.getPolynomial()))

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JGKK · 10 April 2020 07:26

The first code you found is nearly it. It uses an npm module https://www.npmjs.com/package/nerdamer which does exactly what you want. Good find.
Now you have some more Homework.
1st you need to learn how to install external modules so that you can use them in Nodered.
2nd install the Nerdamer Module as per these instructions.
3rd read the documentation of Nerdamer https://nerdamer.com/documentation.html which fortunately seam to be very good and figure out how to use it.
To get you started here is the Nodered documentation on how to use external modules in functions:
https://nodered.org/docs/user-guide/writing-functions#loading-additional-modules

Have fun and stay healthy, Johannes

lalo · 11 April 2020 04:58

Hey @JGKK Johannes Thanks but I'm having troubles to install npm.

npm

JGKK · 11 April 2020 05:14

you are using the wrong command. Use it like it says on the npm website link i posted before https://www.npmjs.com/package/nerdamer on the top right npm i nerdamer

lalo · 11 April 2020 05:35

@JGKK Johannes yeah I realized that the code was in the upper corner. Sorry and Thanks I'm going to try with the nerdamer.

JGKK · 11 April 2020 05:37

you will find this very helpful for what you need to enter in your settings.js file as its otherwise not very clear in the documentation of nerdamer:

edit:
feel free to ask if you have more question as i already have it up and running

lalo · 11 April 2020 20:28

I have a doubt after installing in a page i found that i have to do something like this...

I need some help with that I don' want to mess it up

JGKK · 11 April 2020 20:32

    functionGlobalContext: {
        nerdamer:require('nerdamer/all')
        // os:require('os'),
        // jfive:require("johnny-five"),
        // j5board:require("johnny-five").Board({r$
    },

you can than access it with

const nerdamer = global.get(“nerdamer”);

in a function node

lalo · 11 April 2020 21:24

I don't know if I did something wrong.

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