> df
    NO2 Month
1    23    01
2    27    01
3    16    01
4    13    01
5    26    01
6    23    01
7    51    01
8    46    01
9    21    01
10   18    01
11   13    01
12   22    01
13   47    01
14   60    01
15   49    01
16   76    01
17   38    01
18   24    01
19   15    01
20   20    01
21   33    01
22   17    01
23   19    01
24   20    01
25   25    01
26   46    01
27   53    01
28   41    01
29   54    01
30   28    01
31   28    01
32   51    02
33   61    02
34   56    02
35   57    02
36   30    02
37   12    02
38   27    02
39   13    02
40   35    02
41   40    02
42   40    02
43   47    02
44   72    02
45   55    02
46   30    02
47   10    02
48   29    02
49   50    02
50   39    02
51   61    02
52   56    02
53   44    02
54   46    02
55   35    02
56   34    02
57   41    02
58   39    02
59   39    02
60   27    03
61   48    03
62   36    03
63   40    03
64   41    03
65   45    03
66   46    03
67   43    03
68   55    03 (...)

df=data.frame(data)
df$Month=as.numeric(format(data$date,format="%m"))
df=df%>%select(c("NO2","Month"))

df=reshape(df,idvar=c("NO2","Month"),direction="wide",timevar="Month")
warnings() ## here i have first errors (will show them in below)

df=spread(df,Month,NO2)  ## have problems here also

df=spread(df,df$Month,df$NO2)  ## and here also

1: In reshapeWide(data, idvar = idvar, timevar = timevar,  ... :
  multiple rows match for Month=1: first taken

Error in eval_tidy(enquo(var), var_env) : object 'Month' not found

Error: "var" must evaluate to a single number or a column name, not NULL