ArrayPlot axes ticks and PlotLegends value

Question

My question has two parts:

First Part:

I have the following array:

data = {{0.00545, 0.031286, 0.047969, 0.03371, 0.067131, 0.069519, 0.055705, 
  0.075217}, {0.003295, 0.029857, 0.082773, 0.09734, 0.105596, 
  0.09507, 0.074274, 0.066184}, {0.004738, 0.051967, 0.119394, 
  0.121927, 0.133162, 0.136331, 0.073764, 0.064085}, {0.007415, 
  0.100494, 0.134302, 0.152252, 0.237188, 0.115811, 0.071255, 
  0.053821}, {0.016775, 0.089863, 0.144896, 0.185504, 0.148454, 
  0.103395, 0.064046, 0.026352}, {0.011129, 0.096169, 0.292988, 
  0.138956, 0.125583, 0.097096, 0.052228, 0.035961}, {0.011951, 
  0.486986, 0.09108, 0.081619, 0.088997, 0.040025, 0.017843, 
  0.022213}, {0.042095, 0.033775, 0.029787, 0.043058, 0.018558, 
  0.010313, 0.005565, 0.010936}}

I define the following to change the tickers:

g1 = {"[0,5)", "[5,18)", "[18,30)", "[30,40)", "[40,50)", "[50,60)", 
   "[60,70)", " 70+"};
g2 = Range[8];
g3 = Transpose[{g2, g1}];
g4 = Transpose[{g2 // Reverse, g1}];

I then Plot as:

ArrayPlot[data, ColorFunction -> "Rainbow", PlotTheme -> "Detailed", 
 Mesh -> True, Ticks -> {{g4, None}, {g3, None}}]

However this does not show any tickers, I wonder what am I doing wrong?

Second Part: If you plot using the command I have you see that the plot legends are 0.1, 0.2, 0.3 and 0.4, I wonder how can I change them to my own list {0,2,4,6,8} (as you can see there are two more entries on the list). I do:

ArrayPlot[data, ColorFunction -> "Rainbow", PlotTheme -> "Detailed", 
 Mesh -> True, Ticks -> {{g4, None}, {g3, None}}, 
 PlotLegends -> {0, 2, 4, 6, 8}]

and this gives a plot legend with two tickers of 0 and 2. I wonder what am I doing wrong?

Answer 1

1. Use FrameTicks instead of Ticks and add the option Frame->True.

2. Rescale the in put data to run from 0 to 8.

ArrayPlot[Rescale[data, MinMax@data, {0, 8}], 
 ColorFunction -> "Rainbow", PlotTheme -> "Detailed", Mesh -> True, 
 Frame -> True, FrameTicks -> {{g4, None}, {g3, None}} ]

Add the option PlotLegends -> Range[0, 8] to get