[R] Error in colouring by group in core plot R

[Luigi Marongiu]

Hello,
I am trying to make an epidemic plot of the COVID pandemic using the core
plot function. I am looking at three countries and the countries are as
factors. The idea is to colour the entry by country, following this scheme:
```
df = data.frame(index = 1:10,
                value = c(rnorm(10), rnorm(10), rnorm(10)),
                set = c(rep("Group 1", 3), rep("Group 2", 3), rep("Group
3", 4)))
plot(df$index ~ df$value, col=c("blue", "orange", "purple")[df$set])
```
But in the actual graph there is only one colour:
```
Index = c(1:101)
g1 = c(0,259,457,688,769,1771,1459,1737,1981,2099,2589,2825,3235,3884,3694,

 3143,3385,2652,2973,2467,2015,14108,5090,2641,2008,2048,1888,1749,391,
       889,823,648,214,508,406,433,327,427,573,202,125,119,139,143,99,44,40,

 0,0,0,0,0,0,0,0,0,0,0,0,46,39,78,47,67,55,54,45,0,79,36,35,0,0,0,39,0,
       0,63,42,46,99,108,89,46,46,0,325,0,0,0,0,0,0,0,0,0,0,0,0,0,0)
g2 =
c(0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
       0,0,0,0,0,0,0,59,283,125,130,240,184,341,401,779,930,924,1214,1459,
       2095,2960,2993,4528,2516,2509,4183,3935,4332,6615,6933,6824,4740,
       4450,4923,6173,6813,6365,4933,4031,3252,4288,5633,4939,3936,3281,
       2402,2218,2138,2543,2945,3699,2327,2018,1323,1388,2195,2481,0,0,
       0,0,0,0,0,0)
g3= c(0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,58,
      78,72,94,147,185,234,239,573,335,466,587,769,778,1247,1492,1797,977,
      2313,2651,2547,3497,3590,3233,3526,4207,5322,5986,6557,5560,4789,
      5249,5210,6203,5909,5974,5217,4050,4053,4782,4668,4585,4805,4316,
      3599,3039,3836,4204,3951,4694,4092,3153,3961,2667,3786,3493,3491,
      3047,2256,2729,3370,2646,0,0,0,0,0,0,0,0)
Incidence = c(g1, g2, g3)
Country = c(rep("China", length(Index)), rep("Germany", length(Index)),
            rep("Italy", length(Index)))
df = data.frame(Index, Incidence, Country)
plot(df$Incidence ~ df$Index,
     col = c("red", "black", "blue")[df$Country],
     type = "l", lwd = 2,
     xaxt = "n",
     xlab = expression(bold("Date")),
     ylab = expression(bold("Incidence")),
     main = "Raw values")
```

What am I missing?
Thank you

-- 
Best regards,
Luigi

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