How to change data of an array in javascript?

Question

Considering the following JavaScript code that runs in Node.js is there any way to change the input data according to below statements ?

Since I am a newbie in JS I do not understand if it passes the header meaning pointer or a value .

u_new = u cos(v)
v_new = u sin(v)

    setData (data) {
    if (data.length > 1) {
      this.u.data = data[0].data
      this.v.data = data[1].data
      this._baseLayer.setData([this.u , this.v])
      Layer.prototype.setData.call(this, data)
    }
  },
  setModel (model) {
    let modelHeader = {
      ...
    }
    Object.assign(this.u.header, modelHeader)
    Object.assign(this.v.header, modelHeader)
    Layer.prototype.setModel.call(this, model)
  }

Original inputs u and v are arrays in this format :

This is u data array

["NaN","NaN","NaN","NaN","NaN",0.77,0.76,0.75,0.84,0.94,1.03,1.11,"NaN"]

This is v data array

Note that v values are in degrees while JavaScript's Math read radians.

["NaN","NaN","NaN","NaN","NaN",187.21,189.48,190.58,192.54,194.48,"NaN",197.21,198.09]

I have already tried the following without any success, I can't see any animation running (I animate u-v vectors) :

// radians = degrees * PI / 180
this.u.data = data[0].data * Math.cos(data[1].data * Math.PI / 180) 
this.v.data = data[0].data * Math.sin(data[1].data * Math.PI / 180)

If such a data processing is not possible should I modify the arrays before I pass them as input to JS ?

"without any success" - what does that mean? console errors? Calculation errors? — mplungjan
– mplungjan, Commented Sep 14, 2020 at 11:27
@ mplungjan You are right sir, sorry for not noting what I mean. I just updated the question. I animate u & v vector data. — estamos
– estamos, Commented Sep 14, 2020 at 11:30

mplungjan · Accepted Answer · 2020-09-14 15:08:34Z

1

Do you mean this?

const uRads = ["NaN", "NaN", "NaN", "NaN", "NaN", 0.77, 0.76, 0.75, 0.84, 0.94, 1.03, 1.11, "NaN"]
  .map(deg => deg === "NaN" ? 0 : Math.cos(deg * Math.PI / 180))

const vRads = ["NaN", "NaN", "NaN", "NaN", "NaN", 187.21, 189.48, 190.58, 192.54, 194.48, "NaN", 197.21, 198.09]
  .map(deg => deg === "NaN" ? 0 : Math.cos(deg * Math.PI / 180))


const res = uRads.map((urad, i) => console.log(urad, vRads[i]))

edited Sep 14, 2020 at 15:08

answered Sep 14, 2020 at 11:55

mplungjan

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9 Comments

estamos Over a year ago

u and v json are not only 2 specific files, so they can't be const, there are multiple with 1 - 1 ratio which are loaded by a server folder.

mplungjan Over a year ago

I have no idea what you mean. You can do

this.u.data = ["NaN","NaN","NaN","NaN","NaN",187.21,189.48,190.58,192.54,194.48,"NaN",197.21,198.09].map(deg => deg === "NaN" ? 0 : Math.cos(deg * Math.PI / 180))

if that is what you need

mplungjan Over a year ago

OR you can do this.u.data = uArray.map(deg => deg === "NaN" ? 0 : Math.cos(deg * Math.PI / 180)) if you have the array in a var

estamos Over a year ago

@ mplungjan That works fine, thank you very much. How can I multiply u_new = u cos v ? That's my cos v = data[1].map(deg => deg === "NaN" ? 0 : Math.cos(deg * Math.PI / 180))

mplungjan Over a year ago

Sorry that is just math - that is up to you. I have zero idea what you are trying to do so I just made it possible for you to do whatever it is you need to do

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