Plot markers size, shape and placement in ListPlot

Question

I have the following test data

testData1 = Table[{x, Sqrt[x]}, {x, 0, 4, .2}];
testData2 = Table[{x, x^(1/3)}, {x, 0, 4, .2}];
testData3 = Table[{x, x^(1/5)}, {x, 0, 4, .18}];
testData4 = Table[{x, x^(1/9)}, {x, 0, 4, .18}];

I need to plot the above data using ListPlot with different markers placed inside the plot area.

I used the following code

ListPlot[{testData1, testData2, testData3, testData4}, 
 PlotMarkers -> {{\[FilledCircle], 15}, {\[FilledDiamond], 
    15}, {\[EmptySquare], 15}, {\[FilledSquare], 15}},
 PlotLegends -> Placed[{"a", "b", "c", "d"}, {Left, Top}]]

and got the following results

In the plot, I am not able to change the size of markers in the plot (data points).

How to change the shape, size of the markers both in plot and in legend?

Answer 1

Clear["Global`*"]

testData[1] = Table[{x, Sqrt[x]}, {x, 0, 4, .2}];
testData[2] = Table[{x, x^(1/3)}, {x, 0, 4, .2}];
testData[3] = Table[{x, x^(1/5)}, {x, 0, 4, .18}];
testData[4] = Table[{x, x^(1/9)}, {x, 0, 4, .18}];

If you want the legend labels to scale with the markers:

Manipulate[
 ListPlot[testData /@ Range[4],
  PlotRangePadding -> Scaled[0.05],
  PlotMarkers -> (Style[#, ms] & /@ {●, ◆, □, ■}),
  PlotLegends -> Placed[
    PointLegend[{"a", "b", "c", "d"},
     LegendMarkerSize -> ms,
     LabelStyle -> {FontSize -> ms}],
    Below]],
 {{ms, 15, "Marker Size"}, {Small, Medium, Large, 15, 18}}]

Answer 2

f[s_String] := Style[s, 18];
ListPlot[{testData1, testData2, testData3, testData4},
 PlotMarkers -> {f["\[FilledCircle]"], f["\[FilledDiamond]"], 
   f["\[EmptySquare]"], f["\[FilledSquare]"]}
 , PlotLegends -> Placed[{f["a"], f["b"], f["c"], f["d"]}, {Left, Top}]
 , ImageSize -> Large
 ]