Added freq alignment

src/MagneticResonanceSignals.jl

@@ -82,7 +82,9 @@ export
     hsvd_water_suppression,
     # Phase correction
     ernst,
-    adjust_phase
+    adjust_phase,
+    # Frequency alignment
+    align_frequency!
 
 # High level signal processing
 export

src/processing.jl

@@ -178,3 +178,31 @@ function baseline_als(spectrum::AxisArray, lambda::Float64, p::Float64; niter::I
         AxisArrays.axes(y)
     )
 end
+
+"""
+    align_frequency!(spectrums::AbstractVector)
+
+Align a list of spectrums in a highest peak with first spectrum as a reference. This will
+pad the spectrum with 0s after shifting to retain the original length.
+"""
+function align_frequency!(spectrums::AbstractVector)
+    # Use first spectrum as a reference
+    highest_peak_ref_idx = findmax(spectrums[1])[2]
+    original_length = length(spectrums[1])
+    for idx=2:length(spectrums)
+        highest_peak_idx = findmax(spectrums[idx])[2]
+        shift = highest_peak_idx - highest_peak_ref_idx
+        pads = [0 for i=1:abs(shift)]
+        if shift > 0
+            # Shift left: right-pad
+            push!(spectrums[idx], pads...)
+            spectrums[idx] = spectrums[idx][abs(shift)+1:abs(shift)+original_length]
+            nothing
+        elseif shift < 0
+            # Shift right: left-pad
+            pushfirst!(spectrums[idx], pads...)
+            spectrums[idx] = spectrums[idx][1:end-abs(shift)]
+            nothing
+        end
+    end
+end

test/processing.jl

@@ -95,3 +95,18 @@ end
     @test !(spec_base[1] ≈ abs.(spec)[1])
     @test spec_base[1] ≈ 2.350083f-8
 end
+
+@testset "frequency alignment" begin
+    test_data = [
+        [1, 2, 4, 10, 2, 4, 3],
+        [1, 2, 50, 2, 4, 2, 3],
+        [1, 3, 4, 5, 10, 1, 2]
+    ]
+    align_frequency!(test_data)
+    expected = [
+        [1, 2, 4, 10, 2, 4, 3],
+        [0, 1, 2, 50, 2, 4, 2],
+        [3, 4, 5, 10, 1, 2, 0]
+    ]
+    @test test_data == expected
+end